Chemical constituents and biological activities of Pterocaulon redolens and Cladogynos orientalis

Abstract

Chemical investigation of Pterocaulon redolens (Forst. f) F. Vill. and Cladogynos orientalis Zipp. ex Span. led to the isolation of seven coumarins, three flavonoids and eleven terpenes including three sesquiterpenes, six diterpenes and two triterpenes. The structure determination of these compounds was extensively accomplished by spectroscopic analyses (UV, IR, MS and NMR properties) and by comparison with previously reported data of known compounds. The aerial parts of Pterocaulon redolens provided one new natural coumarin, namely, 2',3'-dihydroxypuberulin [52], six known coumarins identified as 5-methoxy-6,7-methylenedioxycoumarin [9], ayapin [10], sabandinol [23], puberulin [50], 5-methoxyscopoletin [51] and isofraxidin [53] and also gave three known flavonoids, chrysosplenol C [35], luteolin [54] and tomentin [55]. The roots of Cladogynos orientalis yielded a new sesquiterpene, (4S*,7R*,8R*,10S*)-8-hydroxy-alpha-guaiene [56], together with two known sesquiterpenes, spathulenol [57] and cyperenoic acid [64]. In addition, four new diterpenes, namely, 5-[2-(furan-3-yl)ethyl]-1,5,6-trimethyl-1,2,3,4,5,6,7,8-octahydronaphthalene-1-carboxylic acid [58], methyl 9-(furan-3-yl)-2,7,13-trimethyl-4-oxo-10-oxatricyclo[5.3.3.0[superscript 1,6]]trideca-5,8-diene-2-carboxylate [59], 6-[2-(furan-3-yl)ethyl]-1,5,6-trimethyl-10-oxatricyclo[7.2.1.0[superscript 2,7]]dodec-2(7)-en-11-one [62], 6-[2-(furan-3-yl)-2-oxoethyl]-1,5,6-trimethyl-10-oxatricyclo[7.2.1.0[superscript 2,7]]-dodec-2(7)-en-11-one [63], two known diterpenes, chettaphanin I [48] and chettaphanin II [49] and two known triterpenes, acetoxyaleuritolate [60] and taraxerol [61] were afforded. All isolated compounds were evaluated for their cytotoxicity and antimycobacterial activity. It was found that chrysosplenol C [35], chettaphanin II [49], taraxerol [61], 6-[2-(furan-3-yl)ethyl]-1,5,6-trimethyl-10-oxatricyclo- [7.2.1.0[superscript 2,7]]dodec-2(7)-en-11-one [62] were mild to moderate cytotoxic activity.All of them showed weak antimycobacterial activity except chrysosplenol C [35], 2',3'-dihydroxypuberulin [52] and acetoxyaleuritolate [60], which showed no antimycobacterial activity.