Polyherbal therapy is said to be a current pharmacological principle having the advantage of producing maximum therapeutic efficacy with minimum side effects. We assessed the antidiabetic efficacy and hence the impact on biochemical indices of toxicity by a combination of extracts from neem and bitterleaf. Thirty rats, 25 diabetic and 5 non-diabetic rats, were used for the study. The diabetic rats were divided equally into five groups and respectively treated: saline (diabetic control), extracts from neem and bitterleaf combined, neem only, bitterleaf only and chlorpropamide for a 24 day period. After oral administration of the first dose of extract (400 mg kg�1 b.w.) and chlorpropamide (4.286 mg kg� 1 b.w.), blood glucose was monitored in vivo at various time intervals for 9 h, thereafter daily administration continued for 24 days. Whereas single dose treatment with neem only showed peak reduction (28.56%) an hour after, treatments with combined extracts, bitterleaf and chlorpropamide had their peak reductions all at the 7th hour (24.78, 47.31 and 60.51%, respectively). Percentage reductions in blood glucose relative to their initial values at the end of treatment were 71.05, 44.95, 88.63 and 75.83 for combined extract, neem, bitterleaf and chlorpropamide respectively. The decrease in blood glucose for the groups treated with combined extracts and bitterleaf only compared well (p<0.01) with chlorpropamide and non diabetic control, but not with neem alone. Determination of markers of hepatotoxicity in serum including GPT and GOT activities, total protein, albumin and urea indicated that, of the four treatments, neem provides the best protection against hepatic dysfunction. In the group treated with combined extracts these alternate selective advantages of neem and bitterleaf were expressed as a positive synergy, hence more beneficial than individual treatments.

This study evaluated the anti-inflammatory effect of Kaempferia galanga (KG) using an activity-guided approach. KG rhizomes were serially extracted with petroleum ether, chloroform, methanol and water. These extracts (2 g/kg each) were tested for their ability to inhibit carrageenan-induced rat paw edema. The chloroform extract was found to exert the highest inhibition (42.9%) compared to control (p < 0.001), hence it was further fractionated by washing serially with hexane, hexane-chloroform (1:1) and chloroform. The chloroform fraction (1 g/kg) showed the highest inhibitory effect (51.9%, p < 0.001) on carrageenan-induced edema. This chloroform fraction was further fractionated with hexane-chloroform (1:3) and chloroform, and of the two fractions, the hexane-chloroform sub-fraction was the most effective in inhibiting edema (53.7%, p < 0.001). GC-MS analysis of the active sub-fraction identified ethyl-p-methoxycinnamate (EPMC) as the major component, which was re-crystallized. EPMC dose-dependently inhibited carrageenan-induced edema with an MIC of 100 mg/kg. Moreover, in an in vitro study, EPMC non-selectively inhibited the activities of cyclooxygenases 1 and 2, with IC₅₀ values of 1.12 µM and 0.83 µM respectively. These results validate the anti-inflammatory activity of KG which may be exerted by the inhibition of cyclooxygenases 1 and 2. EPMC isolated from this plant may be the active anti-inflammatory agent.

To study the antidiabetic activity of Gynura procumbens (G. procumbens) used in the traditional management of diabetes in Southern Asia. G. procumbens leaves were extracted sequentially with graded percentage of ethanol in water (95%, 75%, 50%, 25% and 0%), and the extracts were tested for antidiabetic activity using acute (7 h), subcutaneous glucose tolerance test and sub-chronic (14 d) test in non-diabetic and streptozotocin-induced diabetic rats. The extracts were further subjected to phytochemical studies. In acute dose (1 g/kg), the extracts significantly lowered fasting blood glucose (FBG) in streptozotocin-induced diabetic rats (P<0.05). However, the FBG-lowering effect of the 25% extract compared to the other extracts, was rapid (47% after 2 h) and the highest: 53%, 53% and 60% in the 3rd, 5th, and 7th h, respectively (P<0.05), comparable only to the effect of metformin. Furthermore, the extracts suppressed peak FBG in subcutaneous glucose tolerance test, but only the 0% and 25% extracts, and metformin sustained the decrease until the 90th min (P<0.05). Moreover, in the 14 days study, the 25% extract exerted the highest FBG-lowering effect, namely 49.38% and 65.43% on days 7 and 14, respectively (P<0.05), similar to the effect of metformin (46.26% and 65.42%). Total flavanoid and phenolic contents in the extracts were found to decrease with increase in polarity of extraction solvents. The composition of reference compounds (chlorogenic acid, rutin, astragalin and kaempferol-3-O-rutinoside) followed a similar trend. G. procumbens contains antidiabetic principles, most extracted in 25% ethanol. Interaction among active components appears to determine the antidiabetic efficacy, achieved likely by a metformin-like mechanism.

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