Chem. Pharm. Bull. 53(11) 1469—1471 (2005)

found in Central and West Asia and in Himalayan regions of Pakistan. Lindelofia stylosa (KAR. & KIR.) is a perennial herb reported to contain pyrrolizidine alkaloids. In continuation of our studies on the biologically active phytochemicals, we investigated the whole herb of L. stylosa of Pakistani origin. The present work resulted in the isolation of compounds 1—7. The structures of the isolated compounds were elucidated mainly with the help of NMR spectroscopic techniques. Three members of the phenyl propanoid class (compounds 1—3) were isolated from the EtOAc fraction of the plant which were identified to be the derivatives of lithospermic acid. New compound 1 was isolated as a brown yellow gum. The compound showed an M at m/z 579.1493 in HR-FABMS (-ve), in agreement with the formula C30H28O12 (Calcd 579.1502). Its IR spectrum showed the presence of an a ,bunsaturated carbonyl system at 1722 cm . The overall spectral data of compound 1 closely resembled the known compound dimethyl lithospermate (2), the only difference between the two compounds being the appearance of signals for O–CH2CH3 moiety in the NMR spectra of 1. The O–CH2CH3 protons appeared as an AB quartet at d 4.14 (J 14.2 Hz, J 7.0 Hz), and a triplet at d 1.19 (J 7.0 Hz), which corresponded to the carbons resonated at d 62.4 and 14.3, respectively. This indicated that compound 1 is an ethyl ester of lithospermic acid. Compound 2 exhibited an M at m/z 565.1343 in the HR-FAB-MS (-ve), which corresponded to the formula C29H26O12 (Calcd 565.1346). The spectral data of compound 2 was found to be identical with the reported dimethyl lithospermate, which was first isolated from Salvia mitiorrhiza. Compound 3 showed an M at m/z 745.1766 in the HRFAB-MS (-ve), suggestive of the formula C38H34O16 (Calcd 745.1768). The overall spectral data of compound 3 was identified as a known methyl ester derivative of lithospermic acid B, which was isolated from Salvia przewalskii. The comparison of Hand C-NMR data and physical data with those reported in the literature, indicated compounds 4—7 were esters of rosmarinic acid (4), Omethyl rosmarinate (5), ethyl rosmarinate (6) and butyl derivative (7). Their isolation from L. stylosa is reported here for the first time. The isolated compounds 1—7 were found to possess radical scavenging properties in DPPH radical assay, among which, compounds 3 and 4 have exhibited the strongest activities. The rosmarinic acid (4) was found to be as active as the standard (3-t-butyl-4-hydroxyanisole). Compound 4 has been reported in previous studies to be potent antioxidant. It increases the prostaglandin E2 production and reduces the production of leukotriene B4 in human polymorphonuclear leukocytes. It is also an inhibitor of complement C3-convertase as well as an inhibitor of lipid peroxidation. Our results have indicated that the derivatives of lithospermic acid, possessing a C-19 lactate moiety, are more active than those without such substituents, such as compounds 1 and 2. The study of antioxidant potentials of compounds 1— 7 was carried out by using Fe -chelating and superoxide scavenging assays. The results demonstrated the selectivity of compounds 3—5 in these two assays, while the others were inactive. Interestingly, compound 3 has shown activity which is comparable to the standard propyl gallate used in the two assays. Our results demonstrated that the rosmarinate ester derivatives 4—5 and compound 3 possess significant antioxidant activities in various assays (see Table 1).