Isolation of Pyranone Derivative and Other Secondary Metabolites from Engelhardia spicata Bark and Immunomodulatory Analysis

Engelhardia spicata locally known as Mauwa in Nepal, is used as the traditional medicine for treating various ailments. Different classes of biologically active compounds are reported from genus Engelhardia. Despite its biological importance, research on E. spicata remains limited. This study was thus conducted to investigate the bioactive chemical constituents of Engelhardia spicata. The methanolic extract of bark from Engelhardia spicata Lesch. ex Blume, on phytochemical investigation afforded 5-hydroxy-4-(hydroxymethyl)- pyran-2-one (1), gallic acid (2), quercetin-3-O-α-L-rhamnopyranoside (3), astilbin (4), myricitrin (5), quercetin-3- O-β-D-glucopyranoside (6), 3,3′-di-O-methylellagic acid-4-O-β-D-xylopyranoside (7), 3,3′-di-O-methylellagic acid (8) and oleanolic acid (9). Their structures were identified by analyzing the spectroscopic data. Flavonoids, gallic acid, ellagic acid and terpenoids have already been reported from genus Engelhardia. Compound 1, pyranone derivative was reported for the first time from genus Engelhardia. It exhibited weak immunomodulatory activity by 25 μg/mL (176 μM) with oxidative burst inhibition of 27.34 ± 2.1%.