Ficus linearifolia Elmer is an endemic Philippine fig tree distributed in the forests of Luzon, Negros, and Leyte at altitudes up to 900 m above sea level [1]. It was earlier considered as a mere variety of Ficus botryocarpa Miq. [2]. This fig tree was first described in 1907 as an erect tree that reaches a height of 20 m and bears linear lanceolate leaves that are more or less scattered but usually confined towards ends of the branchlets. It grows in low damp wooded ground or along streams in deep ravines at the base of Mt. Banahao (Lucban, Luzon Island) at 750 m above sea level [3]. This fig tree is locally known in the Philippines as daing-daing [4]. Ficus triangularis, commonly known as triangular fig and sweetheart tree, is a native to tropical Africa. It was recently introduced in the Philippines as an ornamental tree [5]. This study was conducted as part of our research on the chemical constituents of the genus Ficus. We earlier reported the isolation of a new neohopane [6] from Ficus pumila. We also reported the isolation of terpenoids and sterols from the endemic Philippine trees, Ficus pseudopalma and Ficus ulmifolia [7]. Recently, we reported the isolation of terpenoids and sterols from another endemic Philippine tree, Ficus odorata. -Sitosteryl-3 -glucopyranoside-6-O-palmitate from the leaves of F. odorata exhibited cytotoxicity against human stomach adenocarcinoma cell line (AGS) with 60.28% growth inhibition [8]. There are no reported chemical constituents and biological activities of F. linearifolia and F. triangularis. We report herein the isolation and structure elucidation of 1–9 from the dichloromethane extract of the air-dried leaves of Ficus linearifolia and 4–13 from the leaves of F. triangularis. To the best of our knowledge, this is the first report on the isolation of these compounds from these trees. Silica gel chromatography of the dichloromethane extract of the leaves of F. linearifolia afforded 1–9. The structure of 1 was elucidated by extensive 1D and 2D NMR spectroscopy and confirmed by comparison of their 13C NMR data with those of 11 ,12 -epoxyurs-14-en-3 -yl acetate [9]. The structures of 2–9 were identified by comparison of their 13C NMR data with those reported in the literature for -amyrin (2) [10], -amyrin (3) [10], squalene (4) [11], -sitosterol (5) [12], -stigmasterol (6) [12], polyprenol (7) [13], linoleic acid (8) [14], lutein (9) [15]. The leaves of Ficus linearifolia were collected from the foot of Mt. Banahaw, at around 600 m above sea level (masl), at Avila s Farm, Brgy Palola, Lucban, Quezon, Philippines in March 2012. Voucher specimens were authenticated by Danilo N. Tandang of Philippine National Museum. The air-dried leaves (310 g) of F. linearifolia were soaked in CH2Cl2 for 3 days and then filtered. The filtrate was concentrated under vacuum to afford the crude extract (6 g), which was chromatographed in increasing proportions of acetone in CH2Cl2 at 10% increments by volume as eluents. The CH2Cl2 fraction was rechromatographed (4 ) in petroleum ether to afford 4 (8 mg). The 10% acetone in CH2Cl2 fraction from the chromatography of the crude extract was rechromatographed (3 ) in 7.5% EtOAc in petroleum ether to afford 1 (12 mg). The 20% acetone in CH2Cl2 fraction from the chromatography of the crude extract was rechromatographed (4 ) in 10% EtOAc in petroleum ether to afford 7 (10 mg). The 30% acetone in CH2Cl2 fraction was rechromatographed (3 ) in 15% EtOAc in petroleum ether to afford 8 (15 mg) and a mixture of 2 and 3 (9 mg).
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May 8, 2018
Meng Bai + 6
Open Access