A tocotrienol quinone dimer and xanthones from the leaf extract of Garcinia nigrolineata

Abstract

Four new compounds (1–4) together with six known compounds (5–10) were isolated from the leaf extract of Garcinia nigrolineata. Compound 4 is a rare tocotrienol quinone dimer. The structures were elucidated based on NMR and MS data. All isolated compounds were evaluated for their antibacterial activities.

Introduction

Garcinia is one of the largest genera of the Clusiaceae family. Over 300 species are distributed throughout the tropical and sub-tropical countries [1], with 29 species found in Thailand [2]. Garcinia plants produce a variety of bioactive compounds [[3], [4], [5], [6], [7], [8]], however, xanthones and benzophenones were the most common compounds isolated from this genus [[5], [6], [7], [8], [9], [10], [11]]. These types of compounds have displayed a wide range of biological activities such as anti-bacterial, cytotoxic, anti-HIV, α-glucosidase inhibitory, antioxidant, anti-inflammatory, antimalarial, and anti-pyretic activities [[12], [13], [14], [15], [16], [17], [18], [19]]. G. nigrolineata is a small to medium sized tree widely distributed throughout Malaysia, Thailand and Myanmar. Previous phytochemical investigations, have resulted in the isolation of xanthones along with minor compounds including benzopyran, biphenyl, benzoquinone and isoflavone derivatives, and some of these compounds showed antibacterial activity against MRSA [10, 20. 21]. Herein, we report the isolation and structure elucidation of four new compounds, three xanthones (1–3) and one tocotrienolquinonedimer (4), together with six known compounds (Fig. 1) from the leaf extract of G. nigrolineata collected from an authentic plant growing in our campus. The antibacterial activities of all isolated compounds are also reported.