ABSTRACT
Objective: To determine the anti-diabetic activity of combined aqueous extracts (1:1mixture) of dry leaves of Psidium guajava linn and Moringa oleifera lam as well as to compare the anti-diabetic activity of these plants by in vitro methods. Methods: In vitro alpha amylase inhibitory assay was performed on porcine alpha amylase and the absorbance was measured at 540 nm using a microplate reader and glucose diffusion inhibitory assay using dialysis membrane. Acarbose was used as the standard in the above mentioned methods. Results: The mixture (1:1) of aqueous plant extracts (at a concentration of 100µg/ml) of Psidium guajava linn and Moringa oleifera lam exhibited 72.08333% inhibition with IC50 value of 10.9µg/ml. The leaf extracts of Psidium guajava (at a concentration 100µg/ml) exhibited 71.23288% of a α amylase inhibitory activity with an IC50 values 19.883µg/ml whereas the leaf extracts of Moringa oleifera (at a concentration of 100µg/ml) exhibited 70.58824% of α amylase inhibitory activity with an IC50 value of 27.974 µg/ml. The Acarbose (standard drug) at a concentration of 100µg/ml showed 72.09302% inhibitory effect on the α amylase activity with an IC50 value 8.9µg/ml. In glucose diffusion inhibition assay the mixture of plant extracts exhibited 76.57% inhibition at 150 min which produces more effects than the two plants. The aqueous extract of Psidium guajava leaves exhibited maximum glucose diffusion inhibition (75.32%) at 150 min as well as Moringa oleifera leaf extract showed the maximum inhibition of 73.70% at the same time interval. For acarbose the percentage was 82.74 at 150 min. The interpretation of the results was done by one-way anova method. Conclusion: The combined extract of the leaves of the 2 plants was found to be more effective than individual plant extracts against diabetes. On comparison of two plants Psidium guajava was found to be more active against diabetes than Moringa oleifera. Also the potentiation effect shown by the combination of extract may be due to synergistic effect of the phytochemical constituents. As the 1:1 mixture of the aqueous extract is found to be more active, the combination of the two plants can be used to formulate drugs for treating diabetes.