Potential Use of Quercus dalechampii Ten. and Q. frainetto Ten. Barks Extracts as Antimicrobial, Enzyme Inhibitory, Antioxidant and Cytotoxic Agents

Abstract

The bark resulted as a by-product after different Quercus sp. processing is a valuable alternative source of phenolic compounds (mainly tannins). Hence, the focus of the present work was to obtain eight extracts from the rhytidome of the less-studied Q. dalechampii and Q. frainetto and characterize them in terms of chemical and bioactive profiles. Ultrasound and microwave-assisted extraction methods were used for the preparation of the extracts. Total phenolic and tannin contents were assessed through classic spectrophotometric methods, while several individual phenolic compounds were identified and quantified using UPLC-PDA. Antioxidant, enzyme-inhibitory, antibacterial, and cytotoxic activities were tested using in vitro assays; additionally being evaluated was the ability of the extracts to inhibit the adherence of MRSA to suture wires. The UPLC analysis confirmed the presence of gallic acid, catechin, taxifolin, vanillic acid, epicatechin, and caffeic acid. The results showed that tested extracts were able to exert cytotoxic effects, at 6% and 3% concentrations, on confluent cells. The tested solutions inhibit α-glucosidase activity and the antibacterial potential suggested a mild to moderate effect against the Gram-positive strains. Overall, the obtained results revealed rich phenolic and tannin contents for the extracts obtained from both species through microwave-assisted extraction, probably responsible for their mild antibacterial and cytotoxic effects.

Exploring polyphenols extraction from Thuja occidentalis L. bark: Optimization, phytochemical profiling, and biological evaluation

“…Inhibiting tyrosinase is of interest in the treatment of skin hyperpigmentation caused by overproduction of melanin, with relevance in both pharmaceutical and cosmetic fields. Numerous studies have demonstrated the effectiveness of extracts obtained from the barks of various trees as anti-tyrosinase agents (Tanase et al 2019b(Tanase et al , 2023. The analyzed extract was found to exert weak inhibitory action on this enzyme, given that the literature cites IC50 values of 4.44 μg/mL for the positive control used in this test (kojic acid).…”

“…The inhibitory potential of OpTh on the tyrosinase enzyme, which is involved in various metabolic processes and biochemical reactions, was examined using in vitro tests adapted for a microplate reader (Tanase et al 2023). The metabolic processes in which tyrosinase is involved include protein synthesis, hormone synthesis, neurotransmitter synthesis, pigment synthesis, and melatonin production.…”

“…From the perspective of its potential antidiabetic effects, it was observed that the extract exerted the most significant inhibitory action on α-glucosidase, while α-amylase was poorly inhibited. Considering that the literature associates in vitro antidiabetic potential with an optimal inhibition ratio of 1:3 between the activities of these two enzymes, as well the IC50 values below 100 μg/mL for the positive control (acarbose), it can be concluded that the obtained extract could be considered for further evaluations in order to support its potential use as adjuvant agent in antidiabetic therapy (Tadera et al 2006;Tanase et al 2023).…”