Obesity Research & Clinical Practice (2010) 4, e247—e252
ORIGINAL ARTICLE
Direct effect of khat and garlic extracts on blood lipids contents: Preliminary in vitro study Hesham Abdul Aziz ∗, Yvonne Tze Fung Tan, Kok Khiang Peh, Mun Fei Yam Department of Pharmaceutical Technology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia Received 7 April 2010 ; received in revised form 30 June 2010; accepted 30 July 2010
KEYWORDS Garlic; Khat; Emulsifying property; Cholesterol; Triglycerides
Summary Khat (Catha edulis) as well as garlic (Allium sativum) has a potential effect on reducing the lipid contents of blood. However, a mechanism by which garlic or khat reduces plasma lipids has not been fully investigated. This study aimed to investigate the direct action of khat and/or garlic (in vitro). The effects of extracted khat and/or garlic on human blood constituents (cholesterol and triglycerides) and on vegetable oil were investigated. The results showed that aqueous garlic extract was able to form an emulsion with oil but not khat extract. Even though, either khat or garlic extract has slight effect on reducing lipid contents of blood; a higher reduction was obtained when the extracts were added in combination. The mechanism of garlic on reducing lipids could be explained by its emulsifying property, while the mechanism of khat is by lipolysis. In conclusion, the synergistic effect of garlic and khat extracts opened an interesting area for further investigation on their roles in combating cardiovascular and obesity disorders. © 2010 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.
Introduction Khat (Catha edulis) belongs to the suborder Rosidae and family Celastraceae. The main ingredients of khat leaves include alkaloids, tannins and flavonoids [1—7]. The major alkaloids in fresh khat leaves are cathinone (0.95 mg/g), cathine (1.98 mg/g) and norephedrine (0.54 mg/g) [1—5]. ∗ Corresponding author. Tel.: +60 4 6577888x4086; fax: +60 4 6570017. E-mail address: [email protected] (H.A. Aziz).
The major alkaloid contents of adult or dried khat leaves are cathine and norephedrine at a ratio of approximately 4:1 [1,4,6,7]. The in vivo reducing activity of khat on cholesterol (CS) and triglycerides (TG) was reported and possible mechanisms of actions were suggested [8—11]. Garlic (Allium sativum), on the other hand, belongs to the family Liliaceae. Allicin is one of the most notable organosulfur compounds found in garlic [12,13]. Garlic extracts have been shown to lower plasma CS and TG [14—26]. However, there are also studies that proved otherwise [27—29]. Nevertheless, the
1871-403X/$ — see front matter © 2010 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.orcp.2010.07.001
e248 mechanism by which garlic reduces plasma lipids has not been fully investigated [30]. In view of these aspects, the present study aimed to investigate the direct effect of khat and/or garlic extracts on human blood cholesterol and triglycerides, with special emphasis on their mechanism of action.
Methods Extraction Khat extracts (KE) were prepared and characterized as previously described in our work [31]. Briefly, dried khat leaves were extracted with ethanol (95%) and filtered (Whatman filter paper, no. 1). The ethanol extract was concentrated using a rotary evaporator (EYELA, N-1001S-W, Tokyo, Japan) and frozen at −70 ◦ C for 24 h and dried by lyophilization (Labconco, Kansas City, MO, USA). An amount of 50 mg/kg body weight of khat extract powder (equivalent to an average amount of khat extract consumed by human) was used in this study [31]. The procedure for aqueous garlic extraction followed a modified method described by previous workers [32,33]. Briefly, 10 g of peeled edible portion of garlic was chopped, homogenized at 1000 rpm for 1 min in 20 g of distilled water (1:2 (w/w)). The mixture was left to stand for 3 h before filtering with Whatman paper (no. 1). The aqueous garlic extract at a dose of 50 mg/kg body weight was reported to be an effective dose in reducing blood pressure and anti-aggregatory effect on platelet aggregation [33,34]. For this reason the concentration 50 mg/kg of body weight was used to calculate for the amount of garlic extract to be used in this study. Based on an average adult of 70 kg, having 5 L of blood [35] and the effective dose reported [31,33,34], the amounts of khat and garlic extracts were calculated.
Determination of cholesterol and triglycerides levels Sixty-six plastic lithium heparin tubes were divided into 11 groups (6/group). Ethanol, water, khat extract or garlic extract was added to the tubes (Table 1). Fresh blood collected from healthy male volunteers (BMI = 28.7, HB = 15.5) was added to the tubes (5 mL/tube). All tubes were incubated in a reciprocating shaker bath water (37 ◦ C) for duration of 5 h and centrifuged at 4000 rpm for 10 min. The plasma collected was tested at the Laboratory of Pathology in LAM WAH EE Hospital, Penang,
H.A. Aziz et al. Malaysia. The total cholesterol and triglycerides levels in the plasma samples were determined using the AEROSET system and the ARCHITECT® c8000 system (Abbott Laboratories, Abbott Park, IL, USA). According to the information provided by the manufacturer, the limits of detection of cholesterol and triglycerides are 0.021 and 0.012 mmol/L, respectively. The limits of quantification of cholesterol and triglycerides were 0.161 and 0.071 mmol/L, respectively.
Characterization of the emulsifying property A ternary phase diagram consisting of vegetable oil (palm olein, Seri Murni, Penang, Malaysia), distilled water and garlic or khat extracts was designed at different percentage levels. In each formula, the aqueous phase was first added to the oily phase, and emulsified using a mechanical mixer at ambient temperature. The samples were stored for one day and centrifuged at 3500 rpm for 5 min. The emulsified layers were measured.
Statistical analysis The results were treated statistically using SPSS software (Version 15, USA). One-way analysis of variance was employed to compare the results. When there was a statistically significant difference, post hoc Tukey Honestly Significant Difference (Tukey-HSD) test was applied. Paired t-test was used to compare the control and the corresponding extract formulations. A statistically significant difference was considered when P < 0.05.
Results Plasma cholesterol level When comparing with the blank blood (BB), all the formulations produced reductions in cholesterol level (P < 0.05) (Fig. 1). However, there was no significant difference among the control formulations. The cholesterol reduction effects of garlic and khat alone and in combination were significantly greater than their corresponding control formulations (P < 0.05). The CS reduction effect of khat (K), garlic (G), and khat garlic combinations KG11, KG12, KG21 were 40.32 ± 4.31, 21.67 ± 1.39, 36.00 ± 0.16, 30.54 ± 0.26 and 69.03 ± 1.95%, respectively and were significantly different from the control formulations. In short, the result showed that
Effect of khat and garlic extracts on blood lipids Table 1
e249
The composition of the prepared groups.
Formulation
Code
Ethanol (mL)
Water (mL)
Khat extracta (mL)
Garlic extracta (mL)
Blood (mL)
Blank blood Control ethanol Control water Control ethanol/water (1:1) Control ethanol/water (1:2) Control ethanol/water (2:1) Khat extract Garlic extract Khat extract/garlic extract (1:1) Khat extract/garlic extract (1:2) Khat extract/garlic extract (2:1)
BB E W EW11 EW12 EW21 K G KG11 KG12 KG21
— 1 — 0.5 0.25 0.75 — — — — —
— — 1 0.5 0.75 0.25 — — — — —
— — — — — — 1 — 0.5 0.25 0.75
— — — — — — — 1 0.5 0.75 0.25
5 5 5 5 5 5 5 5 5 5 5
a
The concentrations of khat and garlic extracts are 5 mg/mL.
the reduction in cholesterol was in the order: KG21 > K > KG11, KG12 > G.
the emulsified layers varied from 1 to 8 mm. In contrast, emulsifying property was not shown by khat extract.
Plasma triglycerides level When comparing with the blank blood (BB), increases in triglyceride were observed with E, EW21 and K (P < 0.05), but not with EW11 (P > 0.05). The triglyceride reduction effects of garlic and khat alone and in combination were significantly greater than their corresponding control formulations (P < 0.05). The reduction effect of garlic (G) and khat garlic combinations KG11, KG12, KG21 were 12.38 ± 5.19, 59.87 ± 3.63, 57.32 ± 1.47 and 46.57 ± 6.89%, respectively. The reduction in triglyceride was in the order: KG11, KG12, KG21 > G.
Discussion In our study, khat extract was prepared using ethanol; as such ethanol was also employed in the control formulations E, EW11, EW12 and EW21. It is apparent that triglyceride increase is directly correlated with the amount of ethanol present and the ethanol in the khat extract may overshadow or mask the triglyceride reduction effect of khat. From Fig. 1 can see that both control (E) and khat (K) caused an increase in TG in blood, however when comparing the effect of K with E on triglyc-
Characterization of the emulsifying property As shown in the phase diagram (Fig. 2), emulsified layers were observed with oil ranges from 30 to 60%, water ranges from 10 to 60% and aqueous garlic extract ranges from 10 to 60%. The height of
Figure 1 The percent of change in the plasma level of cholesterol (CS) and triglycerides(TG). Mean ± SD, N = 6.
Figure 2 Phase diagram showing the emulsified layers produced by garlic extract, oil and water.
e250 eride reduction, K is significantly higher than E (P < 0.05). Ethanol may extract the lipid content of blood, which result in increasing the triglycerides [36,37]. In addition, for combination formulations such as KG11, KG12 and KG21, the decrease in triglyceride were much enhanced to about 47—60%. Khat has been used for centuries to alleviate the sensation of hunger [38,39]. Anorexia is a consequence of chewing khat leaves [4,40]. Khat alkaloids have been widely used as appetite suppressants [1,41]. These alkaloids reduced food intake in rhesus monkeys [42,43], in rats [39,44—47], and in guinea pigs [48]. Chewing of khat leaves was reported to decrease the mean body weight of human [9] and baboon by as much as 10% [49]. Oral administration of khat was found to reduce the cholesterol and triglycerides levels [8—11] and enhance lipolysis [50]. The mechanisms of actions of khat on cholesterol and triglycerides levels were proposed by a number of studies [8—11]. They reported that the decrease in plasma cholesterol and triglyceride was due to the stimulating effect of khat on -adrenergic receptors, by activation of adenylate cyclase, conversion of ATP to c-AMP and consequently, increased c-AMP concentration that has stimulatory effect on lipolysis. It was also reported that khat alkaloid enhanced the release of catecholamine from nerve terminals [4], and increased norepinephrine resulting in an increase in lipolysis, energy expenditure, as well as decrease appetite [8]. In addition, khat was reported to enhance lipolysis in vitro and in vivo [50]. On the other hand, several studies reported that fresh garlic has protective actions against cardiovascular disorders including: stroke, coronary artery disease, arteriosclerosis and hypertension [51—53]. They suggested these beneficial effects have partly been attributed to its ability to inhibit platelet aggregation and thromboxane formation [54—56] and its precise mechanism of action is unknown [33]. Also, the fibrinolytic activity of garlic was reported [57,58]. Further studies supported the lowering effect of garlic on blood pressure [26,34,56,58—60] through vasodilatation of arteries [61]. Rendu et al. reported that ajoene (one product of allicin in garlic) decreased microviscosity of the internal region within the lipid bilayer membrane of intact platelets as well as artificial lipid membranes, without affecting the outer hydrophilic moieties of the bilayer [62]. Speculation on garlic’s action on the inhibition of platelet aggregation, inhibition of thromboxane formation, fibrinolysis and reduction of microvis-
H.A. Aziz et al. cosity of lipid bilayer did not provide any answer to the question how does garlic produce these activities? Hence, the present work aimed to provide an answer to this question by investigating the direct effect of garlic on oil. Normally, in a heterogenous system such as oil and water, they will not mix homogenously. However, in the presence of a suitable surface active agent, an emulsion can be formed with one phase dispersed evenly in the other continuous phase. Our result showed that emulsions were formed at optimized ratios of garlic extract, oil and water. The emulsified layers formed were maintained even after several days. The emulsifying property of garlic results in a reduction in surface tension/interfacial tension, formation of stable film around the oil globules and imparts an adequate electrical potential for the mutual repulsion of the oily globules. This may explain the protective actions of garlic against cardiovascular disorders including: stroke, coronary artery disease, arteriosclerosis and hypertension [51—53], platelet aggregation and thromboxane formation [54—58], hypertension [26,34,56,58—60] vasoconstriction [61].
Conclusion In conclusion, garlic, khat and khat garlic combinations showed reduction in blood cholesterol and triglycerides. However, the reduction was more prominent when khat and garlic were used together. The reduction mechanism could be explained by the emulsifying property of garlic and the lipolysis effect of khat. Due to the promising result, suitable controlled release khat/garlic delivery systems are currently being formulated in order to investigate their roles in treating obesity disorders, as well as the associated cardiovascular side effects.
Conflict of interest Microencapsulation of herbal delivery system for treatment of obesity.
Acknowledgments Fellowship from Institute of Postgraduate Studies (IPS) and funding RU-grant (1001/815001) from Universiti Sains Malaysia (USM) are gratefully acknowledged.
Effect of khat and garlic extracts on blood lipids
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[39] Zelger JL, Carlini EA. Anorexigenic effects of two amines obtained from Catha edulis Forsk (Khat) in rats. Pharmacology Biochemistry and Behavior 1980;12:701—5. [40] Halbach H. Medical aspects of the chewing of khat leaves. Bulletin of the World Health Organization 1972;47: 21—9. [41] Kalix P, Braenden O. Pharmacological aspects of the chewing of khat leaves. Pharmacological Reviews 1985;37:149—64. [42] Foltin RW, Schuster CR. Interaction between the effects of intragastric meals and drugs on feeding in rhesus monkeys. Journal of Pharmacology and Experimental Therapeutics 1983;226:405—10. [43] Yanagita T. Studies on cathinones: cardiovascular and behavioral effects in rats and self-administration experiment in rhesus monkeys. NIDA Research Monograph 1979;27:326—7. [44] Eisenberg MS, Maher TJ, Silverman HI. A comparison of the effects of phenylpropanolamine, d-amphetamine and d-norpseudoephedrine on open-field locomotion and food intake in the rat. Appetite 1987;9:31—7. [45] Foltin RW, Woolverton WL, Schuster CR. Effects of psychomotor stimulants, alone and in pairs, on milk drinking in the rat after intraperitoneal and intragastric administration. Journal of Pharmacology and Experimental Therapeutics 1983;226:411—8. [46] Islam MW, Tariq M, Ageel AM, El-Feraly FS, Al-Meshal IA, Ashraf I. An evaluation of the male reproductive toxicity of cathinone. Toxicology 1990;60:223—34. [47] Knoll J. Studies on the central effects of (−)cathinone. NIDA Research Monograph 1979;27:322—3. [48] Jansson T, Kristiansson B, Qirbi A. Effect of khat on uteroplacental blood flow in awake, chronically catheterized, late-pregnant guinea pigs. Journal of Ethnopharmacology 1988;23:19—26. [49] Mwenda JM, Owuor RA, Kyama CM, Wango EO, M’Arimi M, Langat DK. Khat (Catha edulis) up-regulates testosterone and decreases prolactin and cortisol levels in the baboon. Journal of Ethnopharmacology 2006;103:379—84.
[50] Nencini P. Cathinone, active principle of the Khat leaf: its effects on in vivo and in vitro lipolysis. Pharmacological Research Communications 1980;12:855—61. [51] Bordia A, Verma SK, Vyas AK. Effect of essential oil of onion and garlic on experimental atherosclerosis in rabbits. Atherosclerosis 1977;26:379—86. [52] Bordia AK, Joshi HK, Sanadhya YK, Bhu N. Effect of essential oil of garlic on serum fibrinolytic activity in patients with coronary artery disease. Atherosclerosis 1977;28:155—9. [53] Chutani SK, Bordia A. The effect of fried versus raw garlic on fibrinolytic activity in man. Atherosclerosis 1981;38:417—21. [54] Bordia A. Effect of garlic on human platelet aggregation in vitro. Atherosclerosis 1978;30:355—60. [55] Makheja AN, Vanderhoek JY, Bailey JM. Inhibition of platelet aggregation and thromboxane synthesis by onion and garlic. Lancet 1979;1:781. [56] Samson RR. Effects of dietary garlic and temporal drift on platelet aggregation. Atherosclerosis 1982;44:119—20. [57] Arora RC, Arora S, Gupta RK. The long-term use of garlic in ischemic heart disease. An appraisal. Atherosclerosis 1981;40:175—9. [58] Ernst E. Cardiovascular effects of garlic (Allium sativum): a review. Pharmatherapeutica 1987;5:9—83. [59] Silagy CA, Neil HAW. A meta-analysis of the effect of garlic on blood pressure. Journal of Hypertension 1994;12: 463—8. [60] Foushee DB, Ruffin J, Banerjee U. Garlic as a natural agent for the treatment of hypertension: a preliminary report. Cytobios 1982;34:145—52. [61] Pedraza-Chaverri J, Tapia E, Medina-Campos ON, De Los Angeles Granados M, Franco M. Garlic prevents hypertension induced by chronic inhibition of nitric oxide synthesis. Life Sciences 1998;62:PL71—7. [62] Rendu F, Daveloose D, Debouzy JC, et al. Ajoene, the antiplatelet compound derived from garlic, specifically inhibits platelet release reaction by affecting the plasma membrane internal microviscosity. Biochemical Pharmacology 1989;38:1321—8.
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ORIGINAL ARTICLE
Direct effect of khat and garlic extracts on blood lipids contents: Preliminary in vitro study Hesham Abdul Aziz ∗, Yvonne Tze Fung Tan, Kok Khiang Peh, Mun Fei Yam Department of Pharmaceutical Technology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia Received 7 April 2010 ; received in revised form 30 June 2010; accepted 30 July 2010
KEYWORDS Garlic; Khat; Emulsifying property; Cholesterol; Triglycerides
Summary Khat (Catha edulis) as well as garlic (Allium sativum) has a potential effect on reducing the lipid contents of blood. However, a mechanism by which garlic or khat reduces plasma lipids has not been fully investigated. This study aimed to investigate the direct action of khat and/or garlic (in vitro). The effects of extracted khat and/or garlic on human blood constituents (cholesterol and triglycerides) and on vegetable oil were investigated. The results showed that aqueous garlic extract was able to form an emulsion with oil but not khat extract. Even though, either khat or garlic extract has slight effect on reducing lipid contents of blood; a higher reduction was obtained when the extracts were added in combination. The mechanism of garlic on reducing lipids could be explained by its emulsifying property, while the mechanism of khat is by lipolysis. In conclusion, the synergistic effect of garlic and khat extracts opened an interesting area for further investigation on their roles in combating cardiovascular and obesity disorders. © 2010 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.
Introduction Khat (Catha edulis) belongs to the suborder Rosidae and family Celastraceae. The main ingredients of khat leaves include alkaloids, tannins and flavonoids [1—7]. The major alkaloids in fresh khat leaves are cathinone (0.95 mg/g), cathine (1.98 mg/g) and norephedrine (0.54 mg/g) [1—5]. ∗ Corresponding author. Tel.: +60 4 6577888x4086; fax: +60 4 6570017. E-mail address: [email protected] (H.A. Aziz).
The major alkaloid contents of adult or dried khat leaves are cathine and norephedrine at a ratio of approximately 4:1 [1,4,6,7]. The in vivo reducing activity of khat on cholesterol (CS) and triglycerides (TG) was reported and possible mechanisms of actions were suggested [8—11]. Garlic (Allium sativum), on the other hand, belongs to the family Liliaceae. Allicin is one of the most notable organosulfur compounds found in garlic [12,13]. Garlic extracts have been shown to lower plasma CS and TG [14—26]. However, there are also studies that proved otherwise [27—29]. Nevertheless, the
1871-403X/$ — see front matter © 2010 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.orcp.2010.07.001
e248 mechanism by which garlic reduces plasma lipids has not been fully investigated [30]. In view of these aspects, the present study aimed to investigate the direct effect of khat and/or garlic extracts on human blood cholesterol and triglycerides, with special emphasis on their mechanism of action.
Methods Extraction Khat extracts (KE) were prepared and characterized as previously described in our work [31]. Briefly, dried khat leaves were extracted with ethanol (95%) and filtered (Whatman filter paper, no. 1). The ethanol extract was concentrated using a rotary evaporator (EYELA, N-1001S-W, Tokyo, Japan) and frozen at −70 ◦ C for 24 h and dried by lyophilization (Labconco, Kansas City, MO, USA). An amount of 50 mg/kg body weight of khat extract powder (equivalent to an average amount of khat extract consumed by human) was used in this study [31]. The procedure for aqueous garlic extraction followed a modified method described by previous workers [32,33]. Briefly, 10 g of peeled edible portion of garlic was chopped, homogenized at 1000 rpm for 1 min in 20 g of distilled water (1:2 (w/w)). The mixture was left to stand for 3 h before filtering with Whatman paper (no. 1). The aqueous garlic extract at a dose of 50 mg/kg body weight was reported to be an effective dose in reducing blood pressure and anti-aggregatory effect on platelet aggregation [33,34]. For this reason the concentration 50 mg/kg of body weight was used to calculate for the amount of garlic extract to be used in this study. Based on an average adult of 70 kg, having 5 L of blood [35] and the effective dose reported [31,33,34], the amounts of khat and garlic extracts were calculated.
Determination of cholesterol and triglycerides levels Sixty-six plastic lithium heparin tubes were divided into 11 groups (6/group). Ethanol, water, khat extract or garlic extract was added to the tubes (Table 1). Fresh blood collected from healthy male volunteers (BMI = 28.7, HB = 15.5) was added to the tubes (5 mL/tube). All tubes were incubated in a reciprocating shaker bath water (37 ◦ C) for duration of 5 h and centrifuged at 4000 rpm for 10 min. The plasma collected was tested at the Laboratory of Pathology in LAM WAH EE Hospital, Penang,
H.A. Aziz et al. Malaysia. The total cholesterol and triglycerides levels in the plasma samples were determined using the AEROSET system and the ARCHITECT® c8000 system (Abbott Laboratories, Abbott Park, IL, USA). According to the information provided by the manufacturer, the limits of detection of cholesterol and triglycerides are 0.021 and 0.012 mmol/L, respectively. The limits of quantification of cholesterol and triglycerides were 0.161 and 0.071 mmol/L, respectively.
Characterization of the emulsifying property A ternary phase diagram consisting of vegetable oil (palm olein, Seri Murni, Penang, Malaysia), distilled water and garlic or khat extracts was designed at different percentage levels. In each formula, the aqueous phase was first added to the oily phase, and emulsified using a mechanical mixer at ambient temperature. The samples were stored for one day and centrifuged at 3500 rpm for 5 min. The emulsified layers were measured.
Statistical analysis The results were treated statistically using SPSS software (Version 15, USA). One-way analysis of variance was employed to compare the results. When there was a statistically significant difference, post hoc Tukey Honestly Significant Difference (Tukey-HSD) test was applied. Paired t-test was used to compare the control and the corresponding extract formulations. A statistically significant difference was considered when P < 0.05.
Results Plasma cholesterol level When comparing with the blank blood (BB), all the formulations produced reductions in cholesterol level (P < 0.05) (Fig. 1). However, there was no significant difference among the control formulations. The cholesterol reduction effects of garlic and khat alone and in combination were significantly greater than their corresponding control formulations (P < 0.05). The CS reduction effect of khat (K), garlic (G), and khat garlic combinations KG11, KG12, KG21 were 40.32 ± 4.31, 21.67 ± 1.39, 36.00 ± 0.16, 30.54 ± 0.26 and 69.03 ± 1.95%, respectively and were significantly different from the control formulations. In short, the result showed that
Effect of khat and garlic extracts on blood lipids Table 1
e249
The composition of the prepared groups.
Formulation
Code
Ethanol (mL)
Water (mL)
Khat extracta (mL)
Garlic extracta (mL)
Blood (mL)
Blank blood Control ethanol Control water Control ethanol/water (1:1) Control ethanol/water (1:2) Control ethanol/water (2:1) Khat extract Garlic extract Khat extract/garlic extract (1:1) Khat extract/garlic extract (1:2) Khat extract/garlic extract (2:1)
BB E W EW11 EW12 EW21 K G KG11 KG12 KG21
— 1 — 0.5 0.25 0.75 — — — — —
— — 1 0.5 0.75 0.25 — — — — —
— — — — — — 1 — 0.5 0.25 0.75
— — — — — — — 1 0.5 0.75 0.25
5 5 5 5 5 5 5 5 5 5 5
a
The concentrations of khat and garlic extracts are 5 mg/mL.
the reduction in cholesterol was in the order: KG21 > K > KG11, KG12 > G.
the emulsified layers varied from 1 to 8 mm. In contrast, emulsifying property was not shown by khat extract.
Plasma triglycerides level When comparing with the blank blood (BB), increases in triglyceride were observed with E, EW21 and K (P < 0.05), but not with EW11 (P > 0.05). The triglyceride reduction effects of garlic and khat alone and in combination were significantly greater than their corresponding control formulations (P < 0.05). The reduction effect of garlic (G) and khat garlic combinations KG11, KG12, KG21 were 12.38 ± 5.19, 59.87 ± 3.63, 57.32 ± 1.47 and 46.57 ± 6.89%, respectively. The reduction in triglyceride was in the order: KG11, KG12, KG21 > G.
Discussion In our study, khat extract was prepared using ethanol; as such ethanol was also employed in the control formulations E, EW11, EW12 and EW21. It is apparent that triglyceride increase is directly correlated with the amount of ethanol present and the ethanol in the khat extract may overshadow or mask the triglyceride reduction effect of khat. From Fig. 1 can see that both control (E) and khat (K) caused an increase in TG in blood, however when comparing the effect of K with E on triglyc-
Characterization of the emulsifying property As shown in the phase diagram (Fig. 2), emulsified layers were observed with oil ranges from 30 to 60%, water ranges from 10 to 60% and aqueous garlic extract ranges from 10 to 60%. The height of
Figure 1 The percent of change in the plasma level of cholesterol (CS) and triglycerides(TG). Mean ± SD, N = 6.
Figure 2 Phase diagram showing the emulsified layers produced by garlic extract, oil and water.
e250 eride reduction, K is significantly higher than E (P < 0.05). Ethanol may extract the lipid content of blood, which result in increasing the triglycerides [36,37]. In addition, for combination formulations such as KG11, KG12 and KG21, the decrease in triglyceride were much enhanced to about 47—60%. Khat has been used for centuries to alleviate the sensation of hunger [38,39]. Anorexia is a consequence of chewing khat leaves [4,40]. Khat alkaloids have been widely used as appetite suppressants [1,41]. These alkaloids reduced food intake in rhesus monkeys [42,43], in rats [39,44—47], and in guinea pigs [48]. Chewing of khat leaves was reported to decrease the mean body weight of human [9] and baboon by as much as 10% [49]. Oral administration of khat was found to reduce the cholesterol and triglycerides levels [8—11] and enhance lipolysis [50]. The mechanisms of actions of khat on cholesterol and triglycerides levels were proposed by a number of studies [8—11]. They reported that the decrease in plasma cholesterol and triglyceride was due to the stimulating effect of khat on -adrenergic receptors, by activation of adenylate cyclase, conversion of ATP to c-AMP and consequently, increased c-AMP concentration that has stimulatory effect on lipolysis. It was also reported that khat alkaloid enhanced the release of catecholamine from nerve terminals [4], and increased norepinephrine resulting in an increase in lipolysis, energy expenditure, as well as decrease appetite [8]. In addition, khat was reported to enhance lipolysis in vitro and in vivo [50]. On the other hand, several studies reported that fresh garlic has protective actions against cardiovascular disorders including: stroke, coronary artery disease, arteriosclerosis and hypertension [51—53]. They suggested these beneficial effects have partly been attributed to its ability to inhibit platelet aggregation and thromboxane formation [54—56] and its precise mechanism of action is unknown [33]. Also, the fibrinolytic activity of garlic was reported [57,58]. Further studies supported the lowering effect of garlic on blood pressure [26,34,56,58—60] through vasodilatation of arteries [61]. Rendu et al. reported that ajoene (one product of allicin in garlic) decreased microviscosity of the internal region within the lipid bilayer membrane of intact platelets as well as artificial lipid membranes, without affecting the outer hydrophilic moieties of the bilayer [62]. Speculation on garlic’s action on the inhibition of platelet aggregation, inhibition of thromboxane formation, fibrinolysis and reduction of microvis-
H.A. Aziz et al. cosity of lipid bilayer did not provide any answer to the question how does garlic produce these activities? Hence, the present work aimed to provide an answer to this question by investigating the direct effect of garlic on oil. Normally, in a heterogenous system such as oil and water, they will not mix homogenously. However, in the presence of a suitable surface active agent, an emulsion can be formed with one phase dispersed evenly in the other continuous phase. Our result showed that emulsions were formed at optimized ratios of garlic extract, oil and water. The emulsified layers formed were maintained even after several days. The emulsifying property of garlic results in a reduction in surface tension/interfacial tension, formation of stable film around the oil globules and imparts an adequate electrical potential for the mutual repulsion of the oily globules. This may explain the protective actions of garlic against cardiovascular disorders including: stroke, coronary artery disease, arteriosclerosis and hypertension [51—53], platelet aggregation and thromboxane formation [54—58], hypertension [26,34,56,58—60] vasoconstriction [61].
Conclusion In conclusion, garlic, khat and khat garlic combinations showed reduction in blood cholesterol and triglycerides. However, the reduction was more prominent when khat and garlic were used together. The reduction mechanism could be explained by the emulsifying property of garlic and the lipolysis effect of khat. Due to the promising result, suitable controlled release khat/garlic delivery systems are currently being formulated in order to investigate their roles in treating obesity disorders, as well as the associated cardiovascular side effects.
Conflict of interest Microencapsulation of herbal delivery system for treatment of obesity.
Acknowledgments Fellowship from Institute of Postgraduate Studies (IPS) and funding RU-grant (1001/815001) from Universiti Sains Malaysia (USM) are gratefully acknowledged.
Effect of khat and garlic extracts on blood lipids
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