Plicosepalin A, a new antioxidant catechin-gallic acid derivative of inositol from the mistletoe Plicosepalus curviflorus

Abstract

Phytochemical investigation of the semi-parasitic plant, Plicosepalus curviflorus (Loranthaceae) growing in Saudi Arabia resulted in the isolation of a new catechin-gallic acid derivative of inositol, plicosepalin A (1) [(+) catechin-4′-O-(1″-O-galloyl-5″-O-methyl)-myo-inositol], along with seven known compounds: methyl gallate (2), catechin (3), quercetin (4), gallic acid (5), lupeol (6), β-sitosterol (7), and ursolic acid (8). Their structures were elucidated on the basis of spectroscopic analyses, including HRESIMS, ESIMS, 1H and 13C NMR, HSQC, and HMBC, as well as comparison with reported data. The antioxidant and antimicrobial activities of 1 were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the disc diffusion assay, respectively. Compound 1 exhibited potent free radical scavenging activity with an IC50 value of 9.0 ± 0.27 μM. Moreover, significant activities against Staphylococcus aureus and Bacillus subtilis were recorded.