Phenolic profile and biological activities ofMicromeria graeca(L.) Benth. ex Rchb.

Abstract

The medicinal potential of the ethanol extract of Micromeria graeca (L.) Benth. ex Rchb., harvested in Algeria (MG extract), was evaluated by assessing in vitro its antioxidant, antibacterial, and antityrosinase properties. The total phenolic (= 430 ± 30 mg gallic acid equivalent/100 g of dry weight) and flavonoid (= 190 ± 10 mg quercetin equivalent/100 g of dry weight) contents were evaluated by the Folin-Ciocalteu and the aluminium chloride methods, respectively. Silica gel thin-layer chromatography revealed the presence of chlorogenic, caffeic, and rosmarinic acids and diosmin; the presence of these compounds was confirmed by reverse phase high-performance liquid chromatography. The IC 50 values indicate that the ethanol extract of M. graeca is highly potent in neutralizing the 2,2ʹ-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) cation radicals (ABTS •+ ; IC 50 = 30.5 ± 0.9 µg/mL) and the 2,2ʹ-diphenyl-1-picrylhydrazyl radicals (DPPH • ; IC 50 = 65.8 ± 2.4 µg/mL). The MG extract was also very active on a lipid peroxidation model (IC 50 = 23.4 ± 1.9 µg/mL). The superoxide quenching index values (electrochemically measured) were 332 ± 37 (AI 30) and 638 ± 53 µg/mL (AI 50). The studied extract showed a moderate tyrosinase inhibitory activity (IC 50 = 302 ± 62 µg/mL) and a low antibacterial effect while the combination of this extract with antibiotics restored the activities of cefotaxime and streptomycin on resistant Staphylococcus aureus and Pseudomonas aeruginosa.

Evaluating the In Vitro Potential of Natural Extracts to Protect Lipids from Oxidative Damage

“…Emulsification of LA in PB 20 mM pH 7, using Tween-20 (5.6 µg/mL LA and 5.6 µg/mL Tween-20) Mixture of emulsion in PB, water and sample dissolved in 80% methanol [70] Dissolution of LA (8 mM) in Borate buffer 50 mM pH 9 Mixture of previous solution with FeSO 4 , EDTA, H 2 O 2 , sample dissolved in methanol and PB 0.4 M pH 6.75 [126] Dissolution of sodium linoleate in water (16 mM) Mixture of previous solution in PB 50 mM pH 7.4 [127] Dissolution of LA in ethanol, 2.5% (v/v) Mixture of previous solution with distilled water, PB 50 mM pH 7 and sample [74] Ethanol Dissolution of LA (1.3% (v/v)) and NP in ethanol:water 3:1 (v/v) [76] Different methods available to disperse linoleic acid in a medium that is compatible with oxidizing conditions allow the adaptation of the medium for NP dissolution. For instance, the work of Freitas et al [76] used a system mostly composed of ethanol, which might allow the LPIP determination of a wider range of NPs (including some less polar extracts) using water-soluble radical initiators (such as AAPH) or transition metals.…”

“…For instance, the work of Freitas et al [76] used a system mostly composed of ethanol, which might allow the LPIP determination of a wider range of NPs (including some less polar extracts) using water-soluble radical initiators (such as AAPH) or transition metals. In more aqueous systems, the use of saponified linoleic acid (the sodium salt, for instance) to increase water solubility, with [70,73,128] or without [70,126] the addition of a surfactant, might be a solution to test very hydrophilic compounds (such as natural polysaccharides), which are insoluble, even at low concentrations of organic solvents.…”

Phytochemical Composition, Antioxidant and Antimicrobial Activity of the Balkan Endemic Micromeria frivaldszkyana (Degen) Velen. (Lamiaceae)

“…Non L., M. fruticosa (L.) Druce) are well known to contain essential oil and flavonoids [ 36 ]. Brahmi et al observed antibacterial activity of the Micromeria extract against four pathogenic bacteria, E. coli ATCC 25922, P. aeruginosa ATCC 9027, S. aureus ATCC 6538, and S. aureus 100459, the extracts were inactive against all test-microorganisms (MIC ˃ 2000 μg/mL) [ 18 ]. Ali-Shtayeh et al reported that the freeze-dried water extract of M. nervosa (Desf.)…”

“…(origin, Palestine) indicated lowest activity [ 19 ]. According to Brahmi et al nonpolar extracts from plants have been shown more effective antibacterial properties than polar extracts [ 18 ]. Despite the high polyphenol and flavonoid content (26,570.5 ± 291.3 mg/100 g DW and 1564 mg/100 g DW, respectively) of the used extract, we detected antimicrobial activity against only one foodborne pathogen.…”

“…Further, many studies investigated the possible application of plant extracts as natural preservatives. There are several studies on the antiinflammatory and antimicrobial effects of Micromeria against some pathogens [ 8 , 10 , 18 ]. Ali-Shtayeh et al reported that the antimicrobial activity of different Micromeria species’ extracts could be attributed to plant’s phenolic compounds [ 19 ].…”