Diversity of the diterpenes in the leaves of Xylopia laevigata (Annonaceae) and their cytotoxicities

The phytochemical investigation of the hexane extract which was obtained from the leaves of Xylopia laevigata (Annonaceae) produced six terpenes. Among these, five diterpenes named abieta-7,13-dien-3-one, ent-7β-acetoxy-16β-hydroxy-kaurane, 4-epi-cupressic acid, powerol, and labdorffianic acid B, and one oxygenated sesquiterpene, spathulenol. This is the first time these isolated diterpenes from X. laevigata have been described. The different structures belong to the abietane, kaurane, and labdane diterpenoids, and are indicative of the chemical diversity found in X. laevigata. Moreover, the diterpene ent-7β-acetoxy-16β-hydroxy-kaurane is reported herein for the first time as a natural product, and 4-epi-cupressic acid, powerol, and labdorffianic acid B are reported for the first time in the Annonaceae family. The structures of the isolated compounds were established by extensive analyses using 1D and 2D NMR spectroscopy in combination with MS. The cytotoxic activities of compounds abieta-7,13-dien-3-one, spathulenol, 4-epi-cupressic acid, and powerol were evaluated against tumor and non-tumor cell lines, in which spathulenol was found to be the most active, mainly against K562 with an IC50 value of 17.20 μmol L-1.

对平滑木瓣树（Xylopia laevigata，番荔枝科Annonaceae）叶片来源的正己烷提取物开展植物化学研究，共分离得到6种萜类化合物。其中5个为二萜类成分，分别为abieta-7,13-dien-3-one、ent-7β-acetoxy-16β-hydroxy-kaurane、4-epi-cupressic acid、powerol与labdorffianic acid B，另有1个氧化型倍半萜类化合物spathulenol。本研究首次从平滑木瓣树中分离得到上述二萜类化合物。此类化合物的结构分别属于松香烷型（abietane）、贝壳杉烷型（kaurane）以及劳丹烷型（labdane）二萜类，彰显出该植物所蕴含的化学多样性。此外，二萜ent-7β-acetoxy-16β-hydroxy-kaurane为首次报道的天然产物，而4-epi-cupressic acid、powerol及labdorffianic acid B则为首次在番荔枝科植物中被发现。所分离得到的化合物结构均通过一维（1D）核磁共振波谱（NMR spectroscopy）与二维（2D）核磁共振波谱结合质谱（MS）的全面分析得以确证。本研究对abieta-7,13-dien-3-one、spathulenol、4-epi-cupressic acid及powerol的细胞毒活性进行了评估，测试对象涵盖肿瘤细胞系与非肿瘤细胞系；其中spathulenol活性最强，对K562细胞的半最大效应浓度（IC50）为17.20 μmol·L⁻¹。