AIM OF THE STUDY: The present study was carried out to examine the potential modulatory effects of three commercially available active components (asiaticoside, asiatic acid and madecassic acid) and four extracts (aqueous, ethanol, dichloromethane and hexane) of CA on three major cDNA-expressed human cytochrome P450 (CYP) isoforms.
MATERIALS AND METHODS: High-performance liquid chromatography (HPLC)-based enzyme assays, namely tolbutamide 4-methyhydroxylase, dextromethorphan O-demethylase and testosterone 6beta-hydroxylase assays were developed to probe activities of CYP2C9, CYP2D6 and CYP3A4, respectively. Probe substrates were incubated with or without each active component and extract for each isoform, followed by examination of the kinetics parameters, IC(50) and K(i), to characterize modulatory effects.
RESULTS: CYP2C9 was more susceptible to inhibitory effects by CA extracts compared to CYP2D6 and CYP3A4. Moderate degree of inhibition was observed in ethanol (K(i)=39.1 microg/ml) and dichloromethane (K(i)=26.6 microg/ml) extracts implying potential risk of interaction when CYP2C9 substrates are consumed with CA products. The two extracts however showed negligible inhibition towards CYP2D6 and CYP3A4 (IC(50)'s of 123.3 microg/ml and above). Similarly CA aqueous and hexane extracts did not significantly inhibit all three isoforms investigated (IC(50)'s of 117.9 microg/ml and above). Among the active constituents investigated, asiatic acid and madecassic acid appeared to selectively inhibit CYP2C9 and CYP2D6 more than CYP3A4. Of particular interest is the potent inhibitory effect of asiatic acid on CYP2C9 (K(i)=9.1 microg/ml). This signifies potential risk of interaction when substrates for this isoform are taken together with CA products with high asiatic acid content. Inhibitions of asiatic acid with the other isoforms and that of madecassic acid with all isoforms were only moderate (K(i)'s ranged from 17.2 to 84.4 microg/ml). On the other hand, the IC(50) values for asiaticoside were high (1070.2 microg/ml or above) for all three isoforms, indicating negligible or low potential of this compound to modulate CYP enzymatic activity.
CONCLUSION: Centella asiatica extracts and active constituents inhibited CYP2C9, CYP2D6 and CYP3A4 activities with varying potency with CYP2C9 being the most susceptible isoform to inhibition. Significant inhibition was observed for asiatic acid and CA ethanol and dichloromethane extracts, implying involvement of semipolar constituents from CA in the effect. This study suggested that CA could cause drug-herb interactions through CYP2C9 inhibition.
METHODS: In the present study, adult rats (2.5 months old) were fed with 2, 4 and 6 mL/kg body weight of fresh leaf extract of CeA for 2, 4 and 6 weeks, respectively. After the treatment period, the rats were killed, brains were removed and hippocampal neurons were impregnated with silver nitrate (Golgi staining). Hippocampal CA3 neurons were traced using camera lucida, and dendritic branching points (a measure of dendritic arborization) and intersections (a measure of dendritic length) were quantified. These data were compared with those of age-matched control rats.
RESULTS: The results showed a significant increase in the dendritic length (intersections) and dendritic branching points along the length of both apical and basal dendrites in rats treated with 6 mL/kg body weight/day of CeA for 6 weeks. However, the rats treated with 2 and 4 mL/kg body weight/day for 2 and 4 weeks did not show any significant change in hippocampal CA3 neuronal dendritic arborization.
CONCLUSION: We conclude that constituents present in Centella asiatica fresh leaf extract has neuronal dendritic growth-stimulating properties.
PURPOSE: The present work aimed to assess the antidiabetic potential of arjunolic acid (AA) isolated from Terminalia arjuna in type 2 diabetic rats.
STUDY DESIGN: After extraction, isolation and purification, AA was orally administered to type 2 diabetic Sprague Dawley rats to investigate antidiabetic effect of AA.
METHOD: T2DM was induced via single intraperitoneal injection of streptozotocin-nicotinamide (STZ-NIC) in adult male rats. After 10 days, fasting and random blood glucose (FBG and RBG), body weight (BW), food and water intake, serum C-peptide, insulin and glycated hemoglobin (HbA1c) was measured to confirm T2DM development. Dose dependent effects of orally administered AA (25 and 50 mg/kg/day) for 4 weeks was investigated by measuring BW variation, fasting and postprandial hyperglycemia, oral glucose tolerance test (OGTT), and levels of serum HbA1c, serum total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL), high density lipoprotein (HDL), serum and pancreatic C-peptide, insulin, growth differentiation factor 15 (GDF-15), serum and pancreatic inflammatory cytokines.
RESULTS: The oral administration of AA in preclinical model of T2DM significantly normalized FBG and RBG, restored BW, controlled polyphagia, polydipsia and glucose tolerance. In addition, AA notably reduced serum HbA1c, TC, TG, LDL with non-significant increase in HDL. On the other hand, significant increase in serum and pancreatic C-peptide and insulin was observed with AA treatment, while serum and pancreatic GDF-15 were non-significantly altered in AA treated diabetic rats. Moreover, AA showed dose dependent reduction in serum and pancreatic proinflammatory cytokines including TNF-α, IL-1β and IL-6.
CONCLUSION: For the first time our findings highlighted AA as a potential candidate in type 2 diabetic conditions.