Antioxidant and Biological Properties of Bioactive Phenolic Compounds fromQuercus suberL.

Abstract

Phenolic compounds, namely, hydrolyzable tannins and low molecular weight phenolic compounds, were isolated and purified from Portuguese cork from Quercus suber L. Some of these compounds were studied to evaluate their antioxidant activity, including free-radical scavenging capacity (DPPH method) and reducing capacity (FRAP method). All compounds tested showed significant antioxidant activity, namely, antiradical and reducing properties. The antiradical capacity seemed to increase with the presence of galloyl groups. Regarding the reducing capacity, this structure-activity relationship was not so clear. These compounds were also studied to evaluate the growth inhibitory effect on the estrogen responsive human breast cancer cell line (ER+) MCF-7 and two other colon cancer cell lines (Caco-2 and HT-29). Generally, all the compounds tested exhibited, after a continuous exposure during a 48 h period, a dose-dependent growth inhibitory effect. Relative inhibitory activity was primarily related to the number of phenolic hydroxyl groups (galloyl and HHDP moieties) found in the active structures, with more groups generally conferring increased effects, except for HHDP-di-galloyl-glucose. Mongolicain B showed a greater potential to inhibit the growth of the three cell lines tested, identical to the effect observed with castalagin. Since these compounds are structurally related with each other, this activity might be based within the C-glycosidic ellagitannin moiety.

Antioxidant Capacity and Phenolic Contents of Three <i>Quercus</i> Species

“…The antioxidant property of test sample was defined by IC 50 as the inhibitory concentration of the extract necessary for 50% reduction of ABTS and was expressed in mg/mL.…”

“…The assays were carried out in triplicate. The IC 50 values were calculated at which the absorbance was 0.5. Lower IC 50 indicates higher reducing power.…”

“…Moreover, this compound was an inhibitor of human immune deficiency virus (HIV) [48,49]. As a result of inhibiting cell cycle progression and inducing apoptosis, ellagic acid may be considered as a product of cytotoxicity in tumor cells [50]. Chlorogenic acid is an important antioxidant in plants to ameliorate the damaging effects of oxidative stress in plants and hinder degenerative diseases in animals when supplied in their diet [51].…”

Extraction of Polyphenols and Anthocyanins from the Jambul (Syzygium cumini) Fruit Peels

“…Th e ma jo r s tu d ies h av e in v es tig ated an tio xid an t act iv it y fro m e xt ract s o f tea [11], [12], cu rry [13] and fenugreek leaves [14], citrus peels [15] v alerian (Valerianao fficinalis) root, lavender (Lavandulaofficinalis) and lemon balm (Melissa officinalis) leaves, (Alceakurdica) and (Stachyslavandulifolium) flowers [16], Aeglemarmelos leaves [17], wheat bran [18], among others. However, addit ional b iological functions attributed to plant extracts have been analyzed such as antibacterial and antifungal [19], and anti-tu mor [20], [21] activities. Polyphenols may also be present in high amounts in other less studied samples, such as other types of fruits available in certain countries.…”

Bio-guided fractionation of extracts of Geranium robertianum L.: Relationship between phenolic profile and biological activity

“…Compound 30, which was tentatively identified as castalagin or vescalagin, was the main compound of these fractions (23.6 mg/g in FA4 and 31.5 mg/g in FA5, Table 3). The antioxidant and cytotoxic properties of both castalagin and vescalagin have been previously described (Fernandes et al, 2009;Fridrich et al, 2008;Jordão et al, 2012). In each of the fractions FA4, FA5 and FA8 compound 14, an isomer of geraniin, was the second most abundant compound present (9.3, 26.6 and 15.1 mg/g, respectively, Table 3).…”