Seco-Dendrobine-Type Alkaloids and Bioactive Phenolics from <i>Dendrobium findlayanum</i>

Investigation of the 95% EtOH extract of stems of Dendrobium findlayanum afforded four new seco-dendrobines, findlayines A–D (1–4); two known dendrobines, dendrobine (5) and 2-hydroxydendrobine (6); and four new phenolic compounds, dendrofindlaphenols A–C (7, 9, and 10) and 6″-de-O-methyldendrofindlaphenol A (8). Compounds 1 and 2 are the first seco-dendrobines possessing a seven-membered lactam moiety, with 3 and 4 derived from the oxidative cleavage of the C-2–C-3 bond of dendrobine. The structures were established using spectroscopic methods and by comparison with literature data. The absolute configurations of 1–4 were confirmed via single-crystal X-ray diffraction data. Cytotoxic activity assays against HL-60, SMMC-7721, A-549, MCF-7, and SW480 human cancer cell lines revealed IC50 values ranging from 2.3 to 5.3 μM for compound 7, from 19.4 to 34.4 μM for 8, and from 49.4 to 96.8 μg/mL for the EtOAc extract. An assay of the inhibition of NO production with RAW 264.7 cells indicated that 8 had an IC50 value of 21.4 μM, and the EtOAc extract, 10.5 μg/mL. The EtOAc extract possessed DPPH radical scavenging activity of 69.93% at 100 μg/mL.对芬莱石斛（Dendrobium findlayanum）茎部的95%乙醇（95% EtOH）提取物开展研究，从中分离得到4个新的开环石斛碱类（seco-dendrobines）化合物findlayines A–D（1~4）；2个已知石斛碱类化合物：石斛碱（dendrobine，5）与2-羟基石斛碱（2-hydroxydendrobine，6）；以及4个新酚类化合物：dendrofindlaphenols A–C（7、9、10）与6″-去-O-甲基dendrofindlaphenol A（8）。化合物1与2为首例带有七元内酰胺结构的开环石斛碱类化合物，化合物3与4则由石斛碱的C-2-C-3键经氧化断裂衍生得到。所有化合物的结构均通过波谱学方法解析，并结合文献数据比对得以确证；其中化合物1~4的绝对构型通过单晶X射线衍射数据得到确认。针对HL-60、SMMC-7721、A-549、MCF-7及SW480五种人癌细胞系开展的细胞毒活性测试结果显示，化合物7的半数抑制浓度（IC50）范围为2.3~5.3 μM，化合物8的IC50范围为19.4~34.4 μM，乙酸乙酯（EtOAc）提取物的IC50范围为49.4~96.8 μg/mL。采用RAW 264.7细胞进行的一氧化氮（NO）生成抑制实验表明，化合物8的IC50值为21.4 μM，乙酸乙酯提取物的IC50值为10.5 μg/mL。乙酸乙酯提取物在100 μg/mL浓度下的DPPH自由基清除率可达69.93%。