Bioassay Guided Isolation of Active Compounds from Alchemilla barbatiflora Juz.

Abstract

Abstract:The aerial parts of Alchemilla L. species (Rosaceae) are used internally as diuretic, laxative, tonic and externally for wound healing in Turkish folk medicine. Antioxidant effects of the extracts, fractions and isolated compounds from the aerial parts of A. barbatiflora Juz. were investigated with following methods: 1,1-diphenyl-2-picryl-hydrazyl (DPPH), and superoxide radical scavenging (SOD), phosphomolibdenum-reducing antioxidant power (PRAP), ferric-reducing antioxidant power (FRAP) assays. In addition, tyrosinase, α-glucosidase and acetylcholinesterase inhibition activities of samples were analyzed. The methanol extract from the aerial parts of plant was consecutively fractionated into four subextracts; n-hexane, chloroform, and remaining water extracts. Further studies were carried out on the most active water subextract and the fractions obtained from water subextract with column chromatography. Phytochemical studies on active fractions of the water subextract led to the isolation of seven metabolites including catechin (1) and a catechin dimer; procyanidin B3 (2), a flavonol glucuronide; quercetin-3-O-β-D-glucuronic acid (miquelianin) (3) with flavonoid glycosides; quercetin-3-O-β-D-galactoside (hyperoside) (4), quercetin-3-O-β-D-arabinoside (guaiaverin) (5), kaempferol-3-O-β-Dxylopyranoside (6) and kaempferol-3-O-(6″-coumaroyl-β-D-glycoside) (tiliroside) (7). Their structures were elucidated by spectral techniques (1D and 2D NMR). The experimental data verified that procyanidin B3 displayed remarkable enzyme inhibitory activity among the whole isolated compounds.

Natural and synthetic flavonoid derivatives as new potential tyrosinase inhibitors: a systematic review

“…153 Kaempferol, myricetin, quercetin, isorhamnetin, galangin, morin, and their glycosides are the prevalent naturally occurring avonols, mostly found as O-glycosides. [154][155][156][157][158][159][160] So far, several avonols such as quercetin from Olea europaea, kaempferol from Hypericum laricifolium, and Crocus sativus, quercetin-4 0 -O-beta-D-glucoside from Parornix bifurca, quercetin glucopyranoside and kaempferol glucopyranoside from mulberry leaves, morin and 2,3-cis-dihydromorin, 2,3-transdihydromorin from Chloropsis cochinchinensis, were found to act as tyrosinase inhibitors (Table 12). Moreover, it was reported that three 3-hydroxyavones including kaempferol, galangin, and quercetin inhibit the L-DOPA oxidation process catalyzed by tyrosinase, and apparently, this TI activity arises from their Cu 2+ chelating ability.…”

Natural and Bioinspired Phenolic Compounds as Tyrosinase Inhibitors for the Treatment of Skin Hyperpigmentation: Recent Advances

“…A significant melanogenesis inhibition potential has been reported also for galangin (IC 50 = 3.55 µM) [52], isoliquiritigenin (IC 50 = 4.85 µM) [53], kaempferol (IC 50 = 5.5 µM) [54], and dihydromorin (IC 50 = 9.4 µM) [55], belonging to different flavonoid subfamilies, but all characterized by at least one resorcinol moiety. IC50 values in the range 20-150 µM have instead been reported for catechins [56][57][58][59]. Among natural phenolic compounds acting as tyrosinase inhibitors (Supplementary Materials, Table S1), flavonoids are the most representative class.…”

Chemical Constituents Isolated from Lycium shawii and their Chemotaxonomic Significance

“…The obtained methanol extract (304 g) was suspended in water and successively partitioned to provide the following fractions viz., n-hexane (26 g), CH 2 Cl 2 (11 g), EtOAc (25 g), n-BuOH (26 g) and aqueous (44.5 g). The n-hexane fraction was loaded on silica gel column chromatography (CC) and eluted with n-hexane, followed by increasing concentrations of EtOAc in n-hexane (10,20,30, and 100%) to give four fractions H A-D . Fraction H B (0.5 g) was further purified by CC using nhexane:EtOAc (80:20 to 60:40) to provide lyciumate (1, 5 mg) [2], dehydrocostus lactone (2, 60 mg) and costunolide (3, 45 mg) [3], while fraction H A (0.3 g) on further CC purification with nhexane:EtOAc (90:10) as eluent provided nonacosane-10-ol (12, 12 mg) [4].…”

“…On the other hand the occurrence of catechin (4) in the title plant is in agreement with similar types of compounds previously reported from other Lycium species i.e from L. chinens [17]. Importantly, compound 4 is now reported for the first time as being isolated from the genus Lycium while it has previously been reported to be present in various plants of Solanaceae viz., potato (Solanum tuberosum) [18], Amanaga capsicum, Lycopersicon esculentum Mill, Capsicum annuum [19], and Alchemilla barbatiflora Juz [20]. The diester lyciumaside (5) has previously been reported from the title plant [2].…”