Prostaglandin inhibitory and antioxidant components of Cistus laurifolius, a Turkish medicinal plant

As Cistus laurifolius has been used traditionally to treat inflammatory and rheumatic disorders, its leaves were tested for prostaglandin (PG) inhibitory and antioxidant activities. The leaf extract showed both activities, i.e., inhibitory effect at 300 μg/ml on PGE 1- and E 2-induced contractions in guinea pig ileum and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect. The separation guided by the activities shown by these dual assays provided sixteen compounds, 1– 16. Known compounds 1– 12 and 15 were identified as 3- O-methyl quercetin ( 1), 3,7- O-dimethyl quercetin ( 2), genkwanin ( 3), 3,7- O-dimethyl kaempferol ( 4), 3,4′- O-dimethyl quercetin ( 5), apigenin ( 6), 3,4′- O-dimethyl kaempferol ( 7), ellagic acid ( 8), β-sitosterol-3- O-β-glucoside ( 9), quercetin 3- O-α-rhamnoside ( 10), 5- O- p-coumaroyl quinic acid methyl ester ( 11), 1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-α- l-rhamnopyranoxypropyl)-2-methoxyphenoxy]-1,3-propanediol ( 12) and 2,3-dihydro-2-(4′-α- l-rhamnopyranosyloxy-3′-methoxyphenyl)-3-hydroxymethyl-7-methoxy-5-benzofuranpropanol ( 15). New lignan glycosides 13 and 14 were determined to be olivil 9- O-β- d-xyloside and berchemol 9- O-rhamnoside, respectively. Compound 16 was isolated as a 2:1 mixture of two diastereomers, the major one of which was determined to be (7 S,8 R)-dihydrodehydrodiconiferyl alcohol 9′- O-α- l-rhamnoside. The structures were determined by detailed 2D NMR analysis together with NOEDF and CD. PG inhibitory effect was observed in 1, 5, 10, 12 and 16 at 30 μg/ml and antioxidant activity, in 1, 2, 8, 10, 12– 14 and 16.