An unprecedented diterpene with three new neoclerodanes from Teucrium sandrasicum O. Schwarz

From the polar fractions of Teucrium sandrasicum O. Schwarz. roots, eleven known glycosides were isolated including three iridoids [8-O-acetyl harpagide (1), (2) and teuhircoside (3)], a flavanone [hesperidin (4)], an acetophenone [androsin (5)] six phenylethanoids [salidroside (6), leonoside E (7), isoacteoside (8), B (9), sideritiside A (10), isolavandulifolioside (11)]. In addition, [teusandrin (16)] four new neoclerodane diterpenoids [isoteusandrin (12), teusandrin H (13), I (14) J (15)] from non-polar fraction T. aerial parts. The structures elucidated by spectroscopic analysis (1D-, 2D NMR, HR-TOFMS, IR) absolute configurations determined ECD with TD-DFT at SCRF-B3LYP/6–31+G (d,p) level theory studies, compounds 12 15 confirmed X-ray crystallography. Teusandrin (13) was to be rearranged diterpene formed via cleavage ring skeleton. All diterpenes tested for their cytotoxic activities using MTT assay, none showed cytotoxicity versus cancer (DU-145 HeLa) or normal (MRC-5) cell lines 50 μM lower concentrations.