Lanostane derivatives from the leaves and twigs of Garcinia wallichii
Graphical abstract
Four undescribed lanostane triterpenes, wallichinane F-I, were isolated from the leaves and twigs of Garcinia wallichii. The cytotoxic activity of the isolated lanostanes was described.
Introduction
Triterpenes are a large group of naturally occurring secondary metabolites found in many plant species as well as other organisms, such as fungi, bacteria, and marine sponges. Triterpenes have been reported to exhibit diverse biological properties including antitumor, antiviral, antimicrobial, and anti-inflammatory activities (Bui et al., 2016; Jamila et al., 2015; Elfita et al., 2009). Additionally, among privileged structural scaffolds, triterpenes have been studied for their potentials as multiple biological receptor targeting (Callies et al., 2015; Soural et al., 2015; Carvalho et al., 2010).
Garcinia wallichii Choisy, locally known in Thai as “Pawa Som”, is a medium-sized tree in the family of Guttiferae. Preliminary pharmacological screening study showed that the crude methanol (MeOH) extract of its leaves and twigs exhibited anti-inflammatory and analgesic effects (Panthong et al., 2009). Recently, we have isolated six lanostane triterpenes from the n-hexane extract of the fruits of G. wallichii. Among those, wallichinane D induced significant cytotoxicity against various cancer cell lines with ED50 values ranging from 3.91 to 7.63 μM (Hongthong et al., 2016). Herein, we reported the isolation of four previously undescribed lanostane-type triterpenes, wallichinanes F‒I (1‒4) and four known compounds including wallichinanes A (5) and B (6) (Hongthong et al., 2016), friedelin (7) (Escobedo-Martinez et al., 2012), and lupeol (8) (Burns et al., 2000) (Fig. 1) from the n-hexane and ethyl acetate (EtOAc) extracts of the leaves and twigs of G. wallichii. Additionally, cytotoxic effects of some of these isolated compounds against a panel of mammalian cancer cell lines were described. The study on structure-activity relationship was also discussed.
Section snippets
Results and discussion
The bioactive compounds from n-hexane and EtOAc extracts of leaves and twigs of G. wallichii (Supplementary data: Table S1) were separated and purified by means of various chromatographic techniques and crystallization leading to the isolation of eight triterpene derivatives including four previously undescribed lanostanes (1–4) and four known triterpenes (5‒8) (Fig. 1).
Four lanostanes (1‒4) possess unsaturated carboxylic acid side chain as indicated by their UV maximum absorption bands (λmax)
Conclusions
Four previously undescribed lanostane triterpenes, wallichinanes F-I (1-4) and four known triterpenes, wallichinanes A (5) and B (6), friedelin (7) and lupeol (8) were isolated from the leaves and twigs of Garcinia wallichii by using bioassay-guided isolation. The present work reports the new structure of lanostane-type triterpenes isolated from the Garcinia genus. Wallichinanes G (2) and H (3) displayed weak cytotoxicity against several cultured cancer cell lines. Study on structural
General experimental procedures
Melting points (uncorrected) were measured on a digital melting point apparatus (Electrothermal). The infrared spectra were recorded on a Perkin Elmer EX FT-IR spectrophotometer and major bands (νmax) were recorded in wave number (cm-1). The ultra violet spectra were recorded on a JASCO V-530 spectrophotometer and principle bands (λmax) were recorded as wavelength (nanometer, nm) and log ε. The optical rotation was recorded on a JASCO DIP-370 digital polarimeter by using 50 mm microcell. The 1H
Declaration of Competing Interest
The authors declare no conflict of interest.
Acknowledgment
The project was supported by the Center of Excellence for Innovation in Chemistry (PERCH-CIC), the Office of the Higher Education Commission, Mahidol University under the National Research Universities Initiative, and Ministry of Higher Education, Science, Research and Innovation, Thailand.
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