Chemical Constituents of the Stem Bark of Bombax ceiba
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CHEMICAL CONSTITUENTS OF THE STEM BARK OF Bombax ceiba
Jirapast Sichaem,1* Kewalin Inthanon,1 Nutthapol Funnimid,1 Kiettipum Phontree,2 Hoang-Vinh-Truong Phan,3 Thi-Minh-Dinh Tran,3 Nakorn Niamnont,4 Kittiwat Srikittiwanna,4 Suttira Sedlak,5 and Thuc-Huy Duong3*
Bombax ceiba L. (syn. B. malabaricum DC. and Salmalia malabaricum DC.) is commonly known as cotton tree and is widely distributed throughout Africa, Asia, and Australia [1]. The bark of this plant is used in wound healing, while the gum has been used as a remedy for influenza, diarrhea, dysentery, and menorrhagia [2]. Previous phytochemical investigations on the bark of B. ceiba resulted in the isolation of shamimicin, lupeol, mangiferin, epicatechin-7-O-β-xylopyranoside, epicatechin3-O-β-xylopyranoside, shamiminol, stigmasta-3,5-diene, lupenone, (±)-lyoniresinol-2a-O-β-D-glucopyranoside, and opuntiol [3]. During our recent chemical investigation of this plant, 10 compounds, bomcibone (1), scopoletin (2), lupeol (3), glochidonol (4), alphitolic acid (5), salicylic aldehyde (6), gallic acid (7), quercetin (8), luteolin (9), and rutin (10), were isolated from the stem bark of B. ceiba. To the best of our knowledge, compound 1 was assigned as a new natural phthalate derivative [4], whereas 4–6 were isolated from this plant for the first time. The structures of all isolated compounds were identified from their spectroscopic data and comparison with those reported in the literature. Plant Material. The stem bark of B. ceiba were collected in Lampang Province, Thailand, in January 2019. The plant material was identified by Dr. Suttira Sedlak at the Walai Rukhavej Botanical Research Institute, Mahasarakham University, and a voucher specimen was retained as a reference (khumkratok No. 06-19). Extraction and Isolation. The air-dried B. ceiba stem bark (5 kg) was ground into powder and exhaustively extracted at room temperature with MeOH (3 × 10 L). The filtered solution was evaporated under reduced pressure to afford a residue (325 g). This crude extract was subsequently partitioned using solvents of n-hexane and EtOAc to yield n-hexane (50.5 g) and EtOAc (45.5 g) extracts. The EtOAc extract was subjected to silica gel column chromatography (CC) using gradient elution of n-hexane–EtOAc (stepwise 90:10–0:100) to give six fractions (Frs. A–F). Fraction B was rechromatographed by silica gel CC with n-hexane–EtOAc (stepwise 80:20–0:100) as eluent to afford 1 (9.3 mg), 2 (4.5 mg), and 3 (27.3 mg). Fraction C was purified by silica gel CC with CH2Cl2–EtOAc (stepwise 10:0–0:10) as eluent to yield 4 (8.5 mg) and 5 (6.7 mg). Fraction E was subjected to silica gel CC with CH2Cl2–MeOH (stepwise 90:10–0:100) as eluent to give 6 (5.1 mg), 7 (3.3 mg), and 8 (15.6 mg). Fraction F was applied to a Sephadex LH-20 column (100 g) with MeOH to obtain 9 (11.0 mg) and 10 (13.8 mg). Bomcibone (1), white amorphous solid. 1H NMR (400 MHz, CDCl3 , δ, ppm): 3.80–3.82 (4H, m, H-10, 10′), 4.51–4.53 (4H, m, H-9, 9′), 4.72 (4H, s, H-11, 11′), 7.83–7.85 (4H, m, H-3, 3′, 6, 6′), 7.89–7.91 (4H, m,
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