Valorization of Rice Husk (Oryza sativa L.) as a Source of In Vitro Antiglycative and Antioxidant Agents

Abstract

Rice husk is a good source of polyphenols, but it has not been efficiently utilized in food applications yet. Therefore, the aim of this work is to investigate, by in vitro assays, the polyphenolic extract (RHE) capacity of this waste to counteract the protein glycation at different stages of the reaction, correlating this activity with the antiradical properties. A microwave-assisted extraction using hydro-alcoholic solvents was applied to recover husk polyphenols. Extraction parameters were optimized by the design of the experiment. The extract with the highest polyphenolic recovery was obtained at 500 W and 90 °C, using 1:35 g of dry material/mL solvent, 80% ethanol, and a 5 min extraction time. Results highlight the ability of RHE to inhibit the formation of fructosamine in the early stage of glycation with a dose-dependent activity. Furthermore, in the middle stage of the reaction, the highest RHE tested concentration (2.5 mg/mL) almost completely inhibit the monitored advanced glycation end products (AGEs), as well as showing a good trapping ability against α-dicarbonyl intermediates. A strong positive correlation with antioxidant activity is also found. The obtained results are supported by the presence of ten polyphenols detected by RP-HPLC-DAD-ESI-MSn, mainly hydroxycinnamic acids and flavonoids, already reported in the literature as antiglycative and antioxidant agents.

Evaluation of Antibacterial and Antibiofilm Activity of Rice Husk Extract against Staphylococcus aureus

“…Rice (Oryza Sativa L.) husk is the waste resulting from the husking of paddy rice, which is the raw rice after threshing. Using RP-HPLC-DAD-ESI-MSn technology, more polyphenols in the rice husk have been identified, and are mainly hydroxycinnamic acids and flavonoids [12]. The rice husk was provided by an Italian organic farm (Di Cristiana Azienda Agricola, Robbio, Pavia, Italy), dried overnight in oven at 45 • C, minced into powder (particle size lower than 500 µm) and extracted with 80% ethanol (1:35, w/v), at 90 • C, for 5 min using a Microwave Assisted Extraction system (Ethos LEAN, Sorisole, Bergamo, Italy) [12,13].…”

Rice Byproduct Compounds: From Green Extraction to Antioxidant Properties

“…It mainly contains polyphenols possessing well-known antioxidant properties and fibers that have an effect on blood glucose and lipid levels. A potential antiproliferative effect, which is still to be completely explored, on ovarian and colon cancer is probably due to its peptide content [7,14,15]. In addition, rice husk also contains lipophilic compounds (~2%), mainly fatty acids, acylglycerols, and sterols, but their potential remains unexplored [16].…”

“…Other compounds, such as gallic acid, p-hydroxybenzaldehyde, p-hydroxybenzoic acid, syringic acid, and cinnamic acid, have been detected in rice husk from several rice varieties [56]. Among flavonoids, apigenin with a pentosyl and glycosyl moiety and tricin have been identified [15].…”

Recovery of Bound Phenolic Compounds from Rice Hulls via Microwave-Assisted Alkaline Hydrolysis

“…The enzymatic hydrolysis with a cellulase mixture at 50 • C for 24 h as a pretreatment step has been also reported for the liberation of phenolic compounds from rice hulls from Thailand [14]. Even though the use of microwaves has been reported for the extraction of phenolic compounds from various plant materials (e.g., [15][16][17]), their application in the case of rice hulls is limited only to the recovery of free phenolic compounds using ethanol [18] or its mixtures with water [19]. Microwaves act directly on molecules by ionic conduction and dipole rotation leading to fast heating of the solvent and the sample resulting in enhanced mass transfer and extraction efficiency as well as reduced duration and solvent consumption [20].…”