Isolation and Characterization of a New Flavonoid Glucoside from Aerial Parts of Phrynium placentarium

Abstract

A new flavonoid glucoside (1) has been isolated from the aerial parts of Phrynium placentarium (Marantaceae). The structure of 1 was established as 5,2c-dihydroxy-3c,4c-dimethoxyflavone-7-O-E-D-glucopyranoside by means of chemical and spectral data including 2D NMR studies. Compound 1 was examined for antioxidant and PCSK3 (furin) inhibition efficacy because inhibitors of furin are under consideration as therapeutic agents for treating various diseases, including HIV, influenza, dengue fever, etc. Experimental results showed antioxidant activity with EC 50 value of 100 Pg/mL and PCSK3 inhibition activity with EC 50 value of 80 Pg/mL on spectrophometric assays. Keywords: Phrynium placentarium, Marantaceae, flavonoid glucoside.Phrynium placentarium (Marantaceae) is 1-2 m tall, having basal leaf and flowers two per bract; it is white to yellowish white and grows in wet shaded places in forest lands of Bhutan, Indonesia, Myanmar, Philippines, Thailand, Vietnam, and the northeastern part of India [1]. It is used as a traditional medicine of the local tribes for the treatment of renal disorder [2, 3] but has not been phytochemically studied. We have investigated the aerial parts of this plant for the first time and isolated a light yellow colored compound 1. Compound 1 was characterized by chemical and spectroscopic (NMR and mass) methods and identified as a flavonoid glucoside. To the best of our knowledge, compound 1 is a new natural product. As part of our regular work, compound 1 was examined for its antioxidant as well as furin inhibition activity. This article reports the isolation and structure elucidation of 1 from the aerial parts of P. placentarium and its efficacy as an antioxidant as well as PCSK3 (furin) inhibitor.Compound 1 was isolated as yellowish needles from the methanolic extract of aerial parts of P. placentarium via repeated column chromatography and was assigned the molecular formula C 23 H 24 O 12 by HR-FAB-MS (+) 493.6039 [M + H] + (calcd for [M] + 492.6013). The UV spectrum showed O max at 279 and 350 nm, indicating the presence of the flavonoid skeleton in 1. The IR spectrum showed broad absorption at 3612 cm -1 (OH stretching) along with absorption bands at 1650 and 1600 cm -1 (characteristic of chromone carbonyl), also suggesting the flavonoid-like structure of 1.