Angiotensin-Converting Enzyme inhibitory activity and antioxidant properties of Nepeta crassifolia Boiss & Buhse and N. binaludensis Jamzad

This article reports phytochemical and biological studies on Nepeta binaludensis and Nepeta crassifolia. Both species were investigated for their angiotensin-converting enzyme (ACE) inhibitory activity and antioxidant properties through three in vitro models [2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and ferric reducing antioxidant power (FRAP) assay]. Aerial parts were extracted with methanol and partitioned between water and subsequently n-hexane, ethyl acetate and n-butanol. N. binaludensis methanol extract exerted significantly higher reducing power (1.9 μM Fe(II)/g) than did the positive control butylhydroxytoluene (63.2 μM Fe(II)/g) in FRAP assay. The highest DPPH radical scavenging activity was found for N. crassifolia, with IC(50) values of 9.6 and 12.1 µg/mL for ethyl acetate and n-butanol fractions, respectively. n-Butanol fraction of both species showed the highest ACE inhibitory activity, with IC(50) values of 59.3 and 81.7 µg/mL for N. binaludensis and N. crassifolia, respectively. Phytochemical investigations resulted in the isolation of ursolic acid, oleanolic acid, apigenin, luteolin and ixoroside. Apigenin-7-O-glucoside, 8-hydroxycirsimaritin and cirsimaritin were furthermore identified in N. crassifolia ethyl acetate-soluble fraction. Nepetanudoside B was isolated from the n-butanol fraction of N. binaludensis.