Full Length Research Paper

Polyphenols content, antioxidant and antimicrobial activities of extracts of some wild plants collected from the south of Tunisia

Mohamed Bouaziz¹, Abdelhafidh Dhouib¹*, Slim Loukil¹, Makki Boukhris² and Sami Sayadi¹

¹Laboratoire des Bioprocédés, Pôle d’Excellence Régionale AUF, (PER-LBP), Centre de Biotechnologie de Sfax, BP: (1177), 3018 Sfax, Tunisie.

²Laboratoire d’Ecologie Végétale, Département des Sciences de la vie, Faculté des Sciences de Sfax, BP: (802), 3018 Sfax, Tunisie.

*Corresponding author. E-mail: abdelhfidh.douib@cbs.rnrt.tn. Tel.: +21674874452. Fax: +21674874452.

Accepted 6 February, 2009

   Abstract

25 wild plants were collected from the south of Tunisia. The dried aerial parts were extracted under a continuous reflux set-up in a Soxhlet extractor with hexane, ethyl acetate, methanol and water. The extracts were screened for total phenolic content, antioxidant and antimicrobial activities. Total phenolic contents were determined using a spectrophotometric technique, based on the Folin-Ciocalteau reagent and calculated as pyrogallol equivalents (PyE) per 100 g of dry weight (dw). Total phenolic content ranged from traces to 2225 ± 267 mg PyE/100 g dw in Periploca angustifolia hexane extract and Erodium glaucophyllum methanol extract, respectively. Total flavonoids and flavonols were measured by a colorimetric assay and expressed as mg of rutin equivalents (RuE) per 100 g dw and mg of quercetin equivalents (QuE) per 100 g dw respectively. The highest amounts of flavonoids of 315 mg RuE/100 g dw and of flavonols of 63 mg QuE/100 g dw was recorded in the ethyl acetate extract of Acacia radiana. The antioxidant capacity of all extracts was evaluated with the (1,1-diphenyl-2-picrylhydrazyl, DPPH and 2,2'-azino-bis [3-ethylbenzthiazoline-6-sulphonic acid]) ABTS tests. Several extracts showed antioxidant capacity higher than (butylated hydroxytoluene) BHT. Different trend was observed for each antioxidant system with respect to solvents used. All tested plants showed antimicrobial activity, but this activity depended closely on the nature of the solvent used and of the microorganism tested. Rhanterium suaveolens ethyl acetate extract showed the largest spectre of antibacterial activity and Bassia indica ethyl acetate extract showed the highest antifungal activity. Interestingly, some of the collected plants had a high phenolic content and powerful antioxidant and antimicrobial activities. These plants may serve as sources of antioxidants with new chemotypes and potential beneficial health properties.

Key words: Plant extract, phenolic compound, antioxidant activity, antimicrobial activity.