Isolation, purification, structure elucidation and preliminary investigation of inhibitory activities on protein tyrosine phosphatase 1B (PTP1B) of compounds from the leaves of 'kamandiis' (Garcinia rubra Merr.) and 'bunog' (Garcinia benthami Pierre)
2016
Rojo, J.B.
One compound each from the leaves of 'kamandiis' (Garcinia rubra Merr.) and 'bunog' (Garcinia benthami Pierre) were isolated and purified. The structures of these compounds were elucidated using sup 1 H- and sup 13 C-NMR, IR and mass spectroscopy. The compound isolated from the leaves of Garcinia benthami (F2-11 GB) and Garcinia rubra (F1-11 GR) were found to be friedelin and squalene, respectively. These compounds were subjected to PTP1B inhibitory assay. Kinetic analysis using Michaelis-Menten plotted using GraphPad Prism 7.0 revealed the V sub max of the reaction using 27 mug/mL of friedelin to be 0.0072 +- 0.0002 mM/min and the V sub max of the negative control to be 0.0082 +- 0.0001 mM/min. The results revealed that friedelin can be used as a noncompetitive inhibitor of PTP1B. One way ANOVA using GraphPad Prism 7.0 confirmed that friedelin significantly decreased the V sub max of the reaction against the negative control [F(4,10) = 16.78, p = 0.0002] at the p0.05 level. Docking studies using AutoDock Tools version 4.2.6 supported the experimental noncompetitive mode of inhibition of friedelin. On the other hand, squalene showed no significant effect on both the K sub m and V sub max of the reaction at 30 mug/mL, 10 mug/mL and 1 mug/mL concentration.
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