Phenolic compounds and antioxidant activity of extracts of Ginkgo leaves

Abstract

The aim of the present study was to determine the flavonol contents of crude extracts from Ginkgo (Ginkgo biloba L.) leaves, their antioxidant properties in model system studies, and their inhibitory action of linoleic acid oxidation in an emulsion system and of triacylglycerols (TAG) in rapeseed oil. Extracts were prepared from both green and yellow leaves of Ginkgo trees using water, aqueous acetone, and ethanol. Extracts were analyzed by HPLC for their presence and content of selected flavonols; these included myricetin, quercetin, kaempferol, isorhamnetin, and morin. The highest level of flavonols, especially quercetin, myricetin and kaempferol, were found in the aqueous acetonic extracts. Crude extracts from yellow Ginkgo leaves contained greater amounts of flavonols. The best DPPH radical-scavenging activity amongst the Ginkgo extracts examined was determined for aqueous acetonic extracts, while the lowest was noted for the ethanolic extract of green leaves. Water infusion extracts exhibited the highest iron(II) chelating activity. The reducing power of extracts from yellow leaves was 2 higher than that of crude extracts from green leaves. Nevertheless, extracts from green Ginkgo leaves imparted a greater protection factor against TAG oxidation, as assessed by the Rancimat method. Crude extracts from yellow Ginkgo leaves were more efficacious than green ones at inhibiting oxidation of the linoleic acid emulsion.

Differences in antioxidant properties of ginkgo leaves collected from male and female trees

“…For both sexes, aqueous ethanolic extraction resulted in almost three times higher phenolic contents than in water extractions (Table I). Similar data were reported by other authors for water extracts (6,13,14) and alcoholic extracts (15). Although extraction with aqueous ethanol was much more eff ective than water extraction, ginkgo teas are used as herbal teas, that is, as water extracts.…”

Antiradical capacity and polyphenol composition of asparagus spears varieties cultivated under diff erent sunlight conditions

“…Preparation of crude extracts 5 g of lyophilized asparagus were extracted with 70 ml of 60% ethanol for 2 h at room temperature according to the methodology described by Kobus et al (2009) with a slight modifi cation. Next, the supernatant was fi ltered using Whatman No 4 paper and rinsed with 50 ml of ethanol.…”

“…The procedure was based on the methodology published by Kobus et al (2009). The phenolic acids were analyzed as a percentage composition using Agilent UPLC equipped with a Bin Pump Infi nity DAD 1290 detector (λ = 260 nm and 310 nm).…”

“…The percentage composition of fl avonols was determined according to the method described by Kobus et al (2009). Extracted fl avonols were separated and identifi ed by Agilent UPLC using a Nova-Pak C18 reversed-phase column (3.9 × 150 mm, 5-μm particle size; both from Waters, Milford, MA, USA).…”

Total phenolic content and antioxidant capacity of ginkgo teas

“…Recently, besides standardized ginkgo extracts, also ginkgo teas are being consumed in high amount. Phenolic content and antioxidant activity of ginkgo leaves and standardized ginkgo extracts were investigated recently (SASAKI et al, 2003;AOSHIMA et al, 2007;MASTEIKOVA et al, 2007;KOBUS et al, 2009;MILOŠEVIĆ et al, 2011). However, the antioxidant properties of commercial ginkgo teas and the effect of preparation method on those were not investigated in details.…”