This review covers the occurrence and biological activities of all natural friedelane triterpenoids found between 1977 and March 2011. The biogeneses of dimeric friedelanes and several rearranged friedelanes are discussed. The pharmacological properties of representative compounds, including celastrol and correolide, have also been compiled, on the basis of 344 references.

Two new polyketide derivatives, huaspenones C and D (1 and 2, resp.), were isolated from the cultures of an endophytic fungus Peyronellaea sp. HS-12, derived from the stems of Huperzia serrata. They share N-bearing furan-3(2H)-one backbone, and 2 has an unprecedented furo[3,2-c]pyridine skeleton. Their structures including the absolute configuration were elucidated by extensive spectroscopic analysis combined with quantum-chemical calculations. (2E,4E)-6-hydroxy-2-methylocta-2,4dienoic acid (3), a key intermediate of the biosynthesis of 1 and 2, was also obtained from the endophyte.Introduction. -Endophytic fungi are microorganisms which spend their life cycle, as a whole or partly, colonizing inter-and/or intra-cellularly inside the healthy tissues of their host plant, typically causing no apparent symptoms of disease [1]. The research on endophytes showed that they are potential sources of novel biologically active secondary metabolites for exploitation in medicine, agriculture, and industry [2 -5]. Furthermore, results from many researches indicated that they could metabolize the same substance as their own host plants [6 -8], rendering them an alternative source of plant secondary metabolites.Huperzia serrata, a Chinese folk medicinal herb, is well-known for the discovery of hupzine A, a potent, highly specific, and reversible inhibitor of acetylcholinesterase [9] [10]. In a previous study, two new furan-3(2H)-one derivatives, huaspenones A and B (4 and 5, resp.), were isolated from Aspergillus sp. XW-12 derived from the stems of H. serrata [11] 1 ). In this work, two novel N-containing furan-3(2H)-one derivatives, 1 and 2, were isolated from the rice culture of an endophytic fungus Peyronellaea sp. HS-12 obtained from the stems of H. serrata, together with a key intermediate of the biosynthesis of 1 and 2, i.e., (2E,4E)-6-hydroxy-2-methylocta-2,4-dienoic acid (3). In addition, two known compounds, andrastin A (4) [13] and huaspenone B (5) [11], were also obtained from the endophytic fungus. Their structures were elucidated by NMR spectroscopy, especially 2D-NMR spectra. The absolute configurations of 1 and 2 were determined by CD analysis, combined with quantum-chemical calculation. To the best of our knowledge, huaspenones C and D (1 and 2, resp.) are the first examples of Nbearing furan-3(2H)-one derivatives in nature, and 2 has an unprecedented furo[3,2c]pyridine skeleton.

Two new triterpenoids, 30-hydroxylup-20(29)-ene 3β-caffeate (1) and 24-nor-friedelan-6α,10-dihydroxy-1,2-dioxo-4,7-dien-29-oic acid (2), together with eight known compounds 3-10, were isolated from the roots of Celastrus stylosus. The structures of these compounds were elucidated on the basis of spectroscopic analyses. To the best of our knowledge, this represents the first study on the chemical constituents of C. stylosus. The antiproliferative activities of the triterpenoids against six human cancer cell lines (PANC-1, A549, PC-3, HepG2, SGC-7901, and HCCLM3) were evaluated. Compounds 3, 4, and 10 exhibited comparable activities against PC-3 and HCCLM3 cell lines as the positive control taxol.

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