LAUSR

Microcos tomentosa Sm. (Syn.: Grewia paniculata L.) is a shrub or small tree that belongs to the Malvaceae family. In northeastern Thailand, its root and stem are used as an ingredient in herbal decoctions to treat jaundice [1], while in the south its leaves are employed to treat herpes simplex and herpes zoster [2]. In Bangladesh, the plant has been used to treat inflammation, respiratory disorders, fever, and diarrhea [3]. Its extracts were shown to possess antibacterial, antidiarrheal, and cytotoxic activities [3, 4]. A previous phytochemical investigation of its roots reported the presence of three triterpenoids, three steroids, a sesquiterpenoid, and two phenolic compounds [5]. In this study, we isolated 10 compounds, friedelin (1) [6], 3 -friedelinol (2) [7], -sitosterol (3) [8], stigmasterol (4) [8], syringaldehyde (5) [9], E-ferulaldehyde (6) [10], scopoletin (7) [11], oleanolic acid (8) [12], 3 -O-trans-ferulyl-2 ,23-dihydroxy-olean-12-en-28-oic acid (9) [13], and 6 -O-hexadecanoyl-D-glucosyl-sitosterol (10) [14], from the leaves and stems of M. tomentosa. All of these compounds, except -sitosterol, were obtained for the first time from this plant. Their identification was performed by comparing their 1H NMR, 13C NMR, and MS data with those reported in the literature. The leaves and stems of M. tomentosa were collected from Khao Hin Son Royal Development Study Centre, Chachoengsao, Thailand, in October 2012 and identified by R. Suttisri. Dried plant parts (1 kg each) were ground and macerated with n-hexane, CH2Cl2, and MeOH (3 L 3, 7 days each). The CH2Cl2 extract of the stems (5 g) was separated on a silica gel column eluted with CH2Cl2–MeOH (49:1 to 3:2) into 10 fractions. Each fraction was further purified on a Sephadex LH-20 column eluted with CH2Cl2–MeOH (3:2). Subsequent purification of fraction 1 on a silica gel column washed down with n-hexane–CH2Cl2 (3:2) afforded 1 (20 mg) and 2 (40 mg). Fraction 2 was further purified on a silica gel column eluted with n-hexane–acetone (17:3) to yield a 10:1 mixture of 3 and 4 (67.9 mg). Separation of fraction 3 on a silica gel column eluted with CH2Cl2–MeOH (99:1) gave a 2:1 mixture of 5 and 6 (4.4 mg), and 7 (3 mg). Fraction 4 was fractionated on a silica gel column eluted with n-hexane–acetone (4:1) to yield 8 (4.3 mg), whereas purification of fraction 5 on a silica gel column washed down with n-hexane–acetone (7:3) afforded 9 (13.7 mg). Fractionation of the CH2Cl2 extract of the leaves (5.9 g) on a silica gel column eluted with CH2Cl2–MeOH (1:0 to 4:1) gave 10 fractions. Repeated chromatography of fraction 7 on a Sephadex LH-20 columns using CH2Cl2–MeOH (1:1) as eluent, followed by a silica gel column eluted with CH2Cl2–MeOH (93:7), furnished 10 (30.1 mg). 3 -O-trans-Ferulyl-2 ,23-dihydroxyolean-12-en-28-oic Acid (9). C40H56O8, white powder. HR-TOF-MS m/z: 687.3858 [M + Na]+. 1H NMR (500 MHz, CDCl3, , ppm, J/Hz): 7.67 (1H, d, J = 16.0, H-7 ), 7.07 (1H, dd, J = 8.0, 2.0, H-6 ), 7.02 (1H, d, J = 2.0, H-2 ), 6.91 (1H, d, J = 8.0, H-5 ), 6.32 (1H, d, J = 16.0, H-8 ), 5.28 (1H, t, J = 3.3, H-12), 4.80 (1H, d, J = 10.0, H-3), 4.05 (1H, td, J = 10.0, 5.0, H-2), 3.91 (3H, s, 3 -OCH3), 3.35 (1H, d, J = 12.5, H-23a), 2.92 (1H, d, J = 12.5, H-23b), 2.81 (1H, dd, J = 13.5, 4.0, H-18), 1.14 (3H, s, H-27), 1.04 (3H, s, H-25), 0.91 (3H, s, H-30), 0.89 (3H, s, H-29), 0.75 (3H, s, H-26), 0.72 (3H, s, H-24). 13C NMR (125 MHz, CDCl3, , ppm): 181.7 (C-28), 169.1 (C-9 ), 148.3 (C-4 ), 146.8 (C-3 ), 146.5 (C-7 ), 143.8 (C-13), 126.7 (C-1 ), 123.4 (C-6 ), 122.2 (C-12), 114.8 (C-5 ), 114.4 (C-8 ), 109.5 (C-2 ), 79.9 (C-3), 66.6 (C-2), 64.6 (C-23), 56.0 (3 -OCH3), 47.5 (C-9), 46.7 (C-5), 46.6 (C-17), 46.4 (C-1), 45.8 (C-19), 43.7 (C-4), 41.7 (C-14), 41.0 (C-18), 39.4 (C-8), 38.0 (C-10), 33.8 (C-21), 33.0 (C-29), 32.4 (C-7), 32.1 (C-22), 30.7 (C-20), 27.6 (C-15), 26.0 (C-27), 23.6 (C-16), 23.5 (C-30), 23.0 (C-11), 17.7 (C-6), 17.4 (C-25), 17.1 (C-26), 13.8 (C-24).