Chemical constituents from selected endemic Philippine cinnamomum species

• Main Author: Espineli, Dinah L.
• Format: text
• Language: English
• Published: Animo Repository 2012
• Subjects: Cinnamomum > Philippines; Extracts; Metabolites; Chemistry
• Online Access: https://animorepository.dlsu.edu.ph/etd_doctoral/1212
• Institution: De La Salle University

Air dried leaves and bark of seven Cinnamomum species namely, Cinnamomum cebuense, Cinnamomum griffithii, Cinnamomum rupestre and Cinnamomum nanophyllum from Cebu, Central Visayas, Philippines and Cinnamomum iners, Cinnamomum utile and Cinnamomum trichophyllum from the Western Visayan region, Philippines were separately homogenized in dichloromethane. The individual extracts were screened and secondary metabolites isolated by silica gel column chromatography. The isolated compounds were characterized and the structures elucidated using extensive 1D and 2D NMR analyses. Forty-five compounds were obtained from the seven Cinnamomum species studied. Some of these compounds are common to several of these species resulting to twenty-four compounds isolated in the study. Two new compounds: a new natural product (CB-14), named 7-isopropyl-3-methoxy-10-methyltricyclo[4.2.2.2]dodeca-3,8-diene-2,5-dione and a new sesquiterpene, CB-5, named 4-(1,4-dimethylhex-4-enyl)-1-methylene-cyclohex-2-ene, along with four known compounds: 4-hydroxy-3-methoxycinnamaldehyde (CB-13), 4-allyl-2-methoxyphenol or eugenol (CB-3), terpineol (CB-2) and humulene (CB-4) were obtained from the DCM extract of the bark of C. cebuense from Bgy. Tabunan, Cebu City by silica gel chromatography. The leaves gave humulene (CBL-6), -caryophyllene (CBL-8), squalene (CBL-2), -amyrin (CBL-3a), -amyrin (CBL-3b) and bauerenol (CBL-3c). The isolates were subjected to antimicrobial and cytotoxicity testing. The antimicrobial tests were conducted at the University of the Philippines - Natural Science Research Institute utilizing seven microorganisms namely: gram-positive bacteria- Staphylococcus aureus and Bacillus subtilis UPCC, gram-negative bacteria- Escherichia coli and Pseudomonas aeruginosa and the fungi- Candida albicans, Trichophyton mentagrophytes and Aspergillus niger. The cytotoxic properties of the isolates were evaluated at the UP Institute of Biology by the 3-(4,5-dimethylthiazol-2-yl)-2,5- 2 diphenyltetrazolium bromide (MTT) assay. The cancer cell lines used were lung adenocarcinoma A549 and colon carcinoma HCT116. Antimicrobial tests for CB-2, CB-3 and CB-4 indicated slight activity against E. coli, P. aeruginosa, S. aureus, B. subtilis, C. albicans and T. mentagrophytes. CB-4 was the most active among the compounds tested against E. coli, P. aeruginosa, S. aureus, C. albicans and T. mentagrophytes, while CB-2 exhibited the highest activity against B. subtilis, even surpassing the activity of the standard antibiotic, Chloramphenicol. Five of the compounds, namely: CB-2, CB-3, CB-4, CB-13 and CB-14 were evaluated for cytotoxicity using the MTT assay. The compounds were tested against a human cancer cell line, colon carcinoma (HCT 116). CB-13 showed moderate activity (IC50 = 18.8004), CB-4 suggested minimal activity (IC50 = 33.0624), while CB-14 was almost non-toxic with IC50 value of 45.5380 against this cell line. The rest of the compounds tested (CB-2 and CB-3) were inactive against HCT 116. Samples which gave positive results in HCT 116 were further tested for cytotoxicity against non-small cell lung adenocarcinoma (A549). CB-4 showed slight activity (IC50 = 23.1964) against this cell line, while CB-13 indicated minimal activity (IC50 = 42.9409). The dichloromethane extract of the bark of Cinnamomum griffithii Meisn. from Argao, Cebu afforded 1,4,7-trihydroxyeudesmane (C-7), 4-hydroxy-5,7,3-trimethoxyflavan-3-ol (C-12), polyprenol (C-11) and a mixture of -amyrin (C-9a) , -amyrin (C-9b) and bauerenol (C-9c). Another compound, benzyl benzoate (CL-7) was also isolated from the leaves. The structures of C-7, C-12 and CL-7 were elucidated by extensive 1D and 2D NMR spectroscopy, while the structures of the rest of the compounds isolated were identified by comparison of their spectral data with those reported in the literature. The dichloromethane extract of the bark of Cinnamomum rupestre from Carmen, Cebu afforded 4-hydroxy-5,7,3-trimethoxyflavan-3-ol (CI-11), 4-hydroxy-3-methoxycinnamaldehyde (CI-6), and 4-allyl-2-methoxyphenol or eugenol (CI-13). The DCM extract of the bark of Cinnamomum nanophyllum also from Carmen, Cebu City 3 afforded 4-hydroxy-5,7,3-trimethoxyflavan-3-ol (CN-3), 4-hydroxy-3-methoxycinnamaldehyde (CN-5), -sitosterol (CN-4) and trilinolein (CN-9). The DCM extract of the leaves of C. rupestre and C. nanophyllum afforded -sitosterol (CIL-2). The structures of the compounds isolated were identified by comparison of their NMR data with those reported in the literature. The dichloromethane extract of the bark of Cinnamomum iners from Guimaras island afforded 5,7-dimethoxy-3’, 4’-methylenedioxyflavan-3-ol (C8-12) and -sitosterol (C8-11). -sitosterol (C8T-4) was also obtained from the DCM extract of the stems of C. iners together with 4-(4-hydroxy-3-methoxyphenyl) but-3-en-2-one (C8T-1/ C8T-7 Minor), cinnamaldehyde (C8T-10), vanillin (C8T-7 Major) and linoleic acid (C8T-8). The leaves of C. iners afforded eugenol (C8L-1), linoleic acid (C8L-8) and -sitosterol (C8L-11). The structures of C8-12, C8T-1 and C8T-10 were elucidated by extensive 1D and 2D NMR spectroscopy, while the structures of the rest of the compounds isolated were identified by comparison of their spectral data with those reported in the literature. The dichloromethane extract of the bark of Cinnamomum utiles Kostermans from Makbak, Iloilo afforded 3,4-dimethoxycinnamyl alcohol (C6-18), 3,4-dimethoxyphenylprop-1-ene (C6-17 Major), eugenol (C6-17 Minor), safrole (C6-3), -sitosterol (C6-7 Major) and stigmasterol (C6-7 Minor). The leaves of Cinnamomum utile yielded (-)-selin-11-en-4α-ol (C6L-8), polyprenol (C6L-10) and -sitosterol (C6L-16) which was also obtained from the DCM extract of the twigs as C6T-1. The structures of C6-18 and C6L-8 were elucidated by extensive 1D and 2D NMR spectroscopy, while the structures of the rest of the compounds isolated were identified by comparison of their spectral data with those reported in the literature. The dichloromethane extract of the leaves of Cinnamomum trichophyllum Quis. & Merr. from Jamindan, Capiz afforded 4-allyl-2-methoxyphenol or eugenol (C7L-6), -sitosterol (C7L-9) and polyprenol (C7L-10). The bark of Cinnamomum trichophyllum yielded trilinolein (C7-4) and a mixture of -sitosterol and stigmasterol (C7-1). The 4 structures of the compounds isolated were identified by comparison of their 1H and 13C NMR spectral data with those reported in the literature. Eugenol is present in five of the seven species namely: C. cebuense, C. rupestre, C. iners, C. trichophyllum and C. utile. β-sitosterol is also present in five Cinnamomum species studied: C. nanophyllum, C. rupestre, C. iners, C. trichophyllum and C. utile. Polyprenol was found to be present in C. griffithii, C. trichophyllum and C. utile, while 4-hydroxy-5,7,3-trimethoxyflavan-3-ol was present in C. griffithii, C. rupestre and C. nanophyllum. Each of the following compounds were found from two Cinnamomum species studied: 4-hydroxy-3-methoxycinnamaldehyde in C. cebuense and C. nanophyllum, trilinolein in C. nanophyllum and C. trichophyllum and stigmasterol in C. trichophyllum and C. utile. Due to the limited amounts of isolates obtained, only C-7, CL-7, C8-12 and C6-3 were tested for cytotoxicity against HCT116. Results indicated that said compounds had no linear interpolation with HCT 116, thus IC50 could not be computed. This implied that these compounds did not exhibit cytotoxic effect against this cell line.