Sixteen lignans with diverse carbon skeletons, including tetrahydrofuran lignans (1, 13–18), 7,9′-dinorlignan (2), dibenzylbutane lignans (9–10), aryl tetrahydronaphthalene lignans (11–12), dihydrobenzofuran neolignans (19–20), 8-O-4′ neolignans (21–22), and six clerodane diterpenoid glucosides (3–8) were isolated from the 70% ethanolic extract of the stems of Tinospora sinensis (Lour.) Merr. Their structures were established by spectroscopic analyses and chemical methods. Among all these isolates, compounds 1–2 and 3–4 were determined as previously undescribed lignans and clerodane diterpenoids respectively, and compounds 9–13 and 17–22 were discovered from T. sinensis for the first time. In addition, it was the first time to report three types of lignans including 7,9′-dinorlignan, dihydrobenzofuran neolignan and 8-O-4′ neolignan from T. sinensis. The biological activities of all isolated compounds were assessed in terms of their nitric oxide production inhibitory activity in LPS stimulated RAW264.7 cells. The results showed that compound 20 exhibited a mild NO production inhibitory effect with an IC50 value of 17.43 ± 2.06 μM.
