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Taking into account the role of reactive oxygen species in the development of inflammation, and the application of the plants of genus Galinsoga Ruiz & Pav. in folk medicines for inflammatory states, we investigated and compared the antioxidant activities of particular Galinsoga extracts and fractions. The compositions of the most active fractions were studied using thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC) methods. The extracts and fractions from Galinsoga parviflora Cav. and Galinsoga quadriradiata Ruiz et Pav. possess dose-dependent free radical-scavenging ability against DPPH• and superoxide radicals, as well as inhibitory effects on linoleic acid peroxidation in a manner comparable to gallic acid. In the most active fractions, flavonoids, patulitrin, quercimeritrin, quercitagetrin and caffeoyl derivatives were detected. Our research demonstrates that the investigated herbs are an interesting source of preparations with significant antioxidant effects. Our results justify the use of both raw materials in inflammatory diseases, among others, due to their ability to prevent free radical-induced deleterious effects.

In this study, for the first time, we used the in vitro metallopeptidase model for the identification of a potential novel activity of defatted evening primrose seed extracts. Prepared extracts of different polarity (aqueous, 60% ethanolic, isopropanolic, and 30% isopropanolic) at concentrations of 1.5-100 microg/mL exhibited a significant and dose dependent inhibition of three tested enzymes. The 50% inhibition of enzymes activity showed that aminopeptidase N (APN) was the enzyme affected to the greatest extent with IC50 at the level of 2.8 microg/mL and 2.9 microg/mL for aqueous and 30% isopropanolic extracts, respectively. The activity of neutral endopeptidase (NEP) was quite strongly inhibited by the extracts as well. The HPLC-DAD analysis and bioguided fractionation led to the identification of four active compounds: (-)-epicatechin gallate, proanthocyanidin B3, oenothein B, and penta-O-galloyl-beta-D-glucose (PGG). Oenothein B has been shown previously to inhibit metallopeptidases. The three other compounds are known to inhibit angiotensin-converting enzyme (ACE), but they have not been previously reported to inhibit the NEP and APN activity. PGG and procyanidins with different degrees of polymerization, as the dominating compounds in O. paradoxa seeds, seemed to play a role in the crude extract activity.

The qualitative analysis of the aqueous extract showed the presence of polyphenolics belonging to different chemical groups: flavan-3-ol derivatives (catechin and procyanidin B 3 ), gallic acid derivatives (gallic acid, ethyl gallate and pentagalloylglucose) and depsides (ellagic acid). The content of total phenolic and procyanidin in extracts depended on the duration of seeds storage and varied from 469 to 388 mg/g and from 436 to 372 mg/g, respectively. The HPLC quantitative analysis of the three main compounds showed that their content varied from 3.70 to 6.18 mg/g for gallic acid, from 23.43 to 18.91 mg/g for (+)-catechin and from 12.50 to 8.02 mg/g for pentagalloylglucose. During seeds storage, the quantity of pentagalloylglucose in extracts decreased by about 30%, while gallic acid content increase was about 30%. The quantity of (+)-catechin has changed less significantly. The scavenging potential of the extracts determined with the DPPH method correlated with the higher concentration of pentagalloylglucose.

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