Chemical Composition, Antioxidant and Enzyme Inhibitory Activities of Onosma bourgaei and Onosma trachytricha and in Silico Molecular Docking Analysis of Dominant Compounds

Abstract

The aim of this study was to investigate the chemical composition, antioxidant and enzyme inhibitory activities of methanol (MeOH) extracts from Onosma bourgaei (Boiss.) and O. trachytricha (Boiss.). In addition, the interactions between phytochemicals found in extracts in high amounts and the target enzymes in question were revealed at the molecular scale by performing in silico molecular docking simulations. While the total amount of flavonoid compounds was higher in O. bourgaei, O. trachytricha was richer in phenolics. Chromatographic analysis showed that the major compounds of the extracts were luteolin 7-glucoside, apigenin 7-glucoside and rosmarinic acid. With the exception of the ferrous ion chelating assay, O. trachytricha exhibited higher antioxidant activity than O. bourgaei. O. bourgaei exhibited also slightly higher activity on digestive enzymes. The inhibitory activities of the Onosma species on tyrosinase were almost equal. In addition, the inhibitory activities of the extracts on acetylcholinesterase (AChE) were stronger than the activity on butyrylcholinesterase (BChE). Molecular docking simulations revealed that luteolin 7-glucoside and apigenin 7-glucoside have particularly strong binding affinities against ChEs, tyrosinase, α-amylase and α-glucosidase when compared with co-crystallized inhibitors. Therefore, it was concluded that the compounds in question could act as effective inhibitors on cholinesterases, tyrosinase and digestive enzymes.

Extraction, Distribution and Diversity of Phenolic Compounds in Most Widespread Boraginaceae Species from Macedonia

“…The content of rosmarinic ( PA15 ) and 5‐cafeoylquinic acid ( PA6 ) was 462.48±5.55 μg/g and 1239.35±24.79 μg/g, respectively, and these values are significantly higher than the previously published data (41.91±1.41 μg/g and 232.93±5.66 μg/g) [8] for O. heterophylla Griseb. On the other hand, when compared to other Onosma species, [16,27] the content of phenolic compounds in the analyzed samples is lower.…”

“…[20] In the extraction mixtures containing methanol and hydrochloric acid (HM and 50HM) the presence of methyl rosmarinate (503.07 � 20. 16 The extraction mixture 50M was shown to be the most efficient for the extraction of flavonoids. The total content of flavonoids was higher in 50M (2525.13 � 13.27 μg/g), followed by 50HM (2085.61 � 1.70 μg/g) and HM (1938.97 � 4.07 μg/g).…”

“…To the best of our knowledge only two flavonols (kaempferol and quercetin 3-O-rutinoside) and two flavones (apigenin and luteolin 7-O-glucosides) have been previously identified in the representatives of Boraginaceae family (Table 2). [32] Apigenin and luteolin derivatives were previously identified in the species of genus Onosma, [16,27] but as 7-O-glucosides, not as C-glucosides. Di-C-glucosides of apigenin and luteolin were not previously described in Boraginacea species.…”

“…In the literature, procedures for extraction of polyphenolic compounds from species that belong to Boraginaceae include use of methanol, ethanol or water, [14][15][16] but also hexane, dichloromethane and ethyl acetate. [16,17] However, very few of them reported experimental methodologies comparing the efficiency of the solvent(s) for extraction of individual polyphenolic components.…”

“…In the literature, procedures for extraction of polyphenolic compounds from species that belong to Boraginaceae include use of methanol, ethanol or water, [14][15][16] but also hexane, dichloromethane and ethyl acetate. [16,17] However, very few of them reported experimental methodologies comparing the efficiency of the solvent(s) for extraction of individual polyphenolic components. Ozer et all., [8] compared the efficiency of ethyl acetate, methanol, and water extracts by measuring the antioxidant and enzyme inhibitory activities of Onosma heterophyllum, and their results have shown the water extracts as most effective.…”