Comparative evaluation of the leaves, fruit pericarp, seeds and bark of Syzygium cumini L. for their phenolic contents, in vitro anti-oxidant and α-glucosidase inhibitory activities.

The different parts of Syzygium cumini (L.) Skeels have been widely studied for their medicinal values, most notably the antidiabetic properties. However, for S. cumini growing in Egypt, no previous study was undertaken to determine the most valuable part regarding the biological activity. This study aims to compare the leaves (L), fruit pericarp (FP), seeds (S), and bark (B) of S. cumini growing in Mansoura, Egypt, based on their total phenolic contents, antioxidant and α-glucosidase inhibition activities. Among the extracts, S demonstrated the highest phenolic content with a value of 337.36 mg gallic acid equivalent (GAE)/g dried extract, followed by B and L showing values of 126.22 and 108.23 mg GAE/g, respectively, while FP showed considerably low phenolic content 26.98 mg GAE/g as compared to the other parts. For ABTS assay, L and S showed high anti-oxidant activity with IC50 values of 3.77 and 5.75 µg/ml, respectively. Meanwhile, B showed comparable anti-oxidant activity (IC50=13.52 µg/ml) to ascorbic acid (IC50=10.67 µg/ml), while FP was the least active (IC50=27.92 µg/ml). Finally, FP was the most active against α-glucosidase with IC50 value of 25.82 µg/ml, followed by S (32.66 µg/ml), while L (60.95 µg/ml) and B (108.49 µg/ml) were much less active, all compared to acarbose (8.5 µg/ml). This study revealed the anti-oxidant and antidiabetic potential of the seeds and fruit pericarp of S. cumini, respectively. Accordingly, a further comprehensive in vivo study is recommended to elucidate the possibility of their use as a functional food or natural supplement.