This review covers literature data summarizing, on one hand, the chemistry of essential oils and, on the other hand, their most important activities. Essential oils, which are complex mixtures of volatile compounds particularly abundant in aromatic plants, are mainly composed of terpenes biogenerated by the mevalonate pathway. These volatile molecules include monoterpenes (hydrocarbon and oxygenated monoterpens), and also sesquiterpenes (hydrocarbon and oxygenated sesquiterpens). Furthermore, they contain phenolic compounds, which are derived via the shikimate pathway. Thanks to their chemical composition, essential oils possess numerous biological activities (antioxidant, anti-inflammatory, antimicrobial, etc…) of great interest in food and cosmetic industries, as well as in the human health field.

Myrtus communis L. (Myrtle) is one of the most important aromatic and medicinal species from the Myrtaceae family. It is traditionally used as antiseptic, disinfectant drug and hypoglycemic agent. The aim of our study was to evaluate the protective effect of Myrtus communis essential oil (McEO) on CCl₄-induced hepatotoxicity in rat. Thirty two adult Wistar rats were divided into 4 groups of 8 each: (1) a control group; (2) was given a single dose of CCl₄ (1 mL kg⁻¹ in 1% olive oil. ip) on the 14^th day (3) were given during 15 days a daily i.p. injection of McEO at 250 mL kg⁻¹ b.w (4) a group was pretreated with McEO and intoxicated with CCl₄ on the 14^th day. The major components of McEO are α-pinene (35.20%), 1,8-cineole (17%), linalool (6.17%) and limonene (8.94%) which accounted for 67.31% of the whole oil. The antioxidant activity of McEO was evaluated using DPPH scavenging ability, β-carotene bleaching inhibition and hydroxyl radical-scavenging activity. Moreover, the effect of McEO (250 mg kg⁻¹ body weight BW) administrated for 14 consecutive days was evaluated in wistar rat. Administration of a single dose of CCl₄ caused hepatotoxicity as monitored by an increase in lipid peroxidation (thiobarbituric acid reactive substances) as well in protein carbonyl level but decreased in antioxidant markers in the liver tissue. The McEO pre-treatment significantly prevented the increased plasma levels of hepatic markers and lipid levels induced by CCl₄ in rats. Furthermore, this fraction improved biochemical and histological parameters as compared to CCl₄-treated group. Our results suggest that M. communis contains promising substances to counteract the CCl₄ intoxication and which may be efficient in the prevention of hepatotoxicity complications.

Astaxanthin (ATX) is a marine carotenoid known for its powerful antioxidant and neuroprotective properties. In this study, we investigated the in vitro and in vivo potential inhibitory effect of ATX on the aldose reductase (AR) activity, a key enzyme in the polyol pathway responsible for the pathogenesis of diabetic complications including diabetic retinopathy (DR). The gerbil Psammomys obesus (P. ob.), an animal model for type 2 diabetes and DR has been used. The erythrocyte and retinal AR activity of P. ob. individuals were, respectively, assessed monthly and at the 7th month during a 7‐month hypercaloric diet (HD) using a NADPH oxidation method. Meanwhile, the body weight and blood glucose of the gerbils were monitored. After 7 months, P. ob. individuals were fed with ATX (4.8 mg/kg of body weight) once a day for 1 week. The results showed that the HD‐fed animals developed significant obesity and hyperglycemia in comparison with controls. Erythrocyte AR activity showed a progressive and significant increase in the HD‐fed group compared with controls. Retinal AR activity was higher in the 7‐month HD‐fed group compared with controls. Erythrocyte AR activity was markedly decreased after ATX‐treatment in vitro and in vivo. These findings suggested that ATX inhibited the erythrocyte AR activity and could be used for DR prevention and/or early treatment.

In the present investigation, essential oil (EO) and methanolic extract of Tunisian Mentha spicata leaves were tested for their chemical composition and biological activities. Results showed that EO was characterized by the predominance of oxygenated monoterpenes (92.18%), followed by monoterpene hydrocarbons and sesquiterpenes whose respective amounts were 2.74 and 3.1% of the whole EO. The main volatile compound of M. spicata EO was L-menthone, accounting for 32.74% of the total volatiles, followed by pulegone (26.67%). The phenolic composition of methanolic extracts was determined by reversed-phase high-performance liquid chromatography. The major flavonoid component was apigenin with a mean concentration of 38.4 mg/100 g dry weight. M. spicata leave extract tested for their antioxidant and antibacterial activities showed a significant antiradical and superoxide anion scavenging capacity in addition to the great potential for antimicrobial activities against the bacteria tested. Spearmint (Mentha spicata L.) is an aromatic plant belonging to the Lamiaceae family. M. spicata L. is commercially cultivated in many regions of the world. Spearmint oil has economical importance and is used in perfumery, confectionary and pharmaceutical preparations. Tunisia is blessed with a rich source of aromatic plants, many of which have not been previously investigated for their chemical constituents and biological potentials. Among these plants, we can mention M. spicata L. (Lamiaceae), which is largely distributed from the humid to the upper arid regions. This work was carried out as a first step for a chemical and biological activity of Tunisian M. spicata through phenolic and essential oil composition. A further isolation and purification of M. spicata phenolics and volatiles will be associated with an application in food industry as antioxidants, additives for food preservation and for enhancing their nutritional value and organoleptic quality. Furthermore, a pharmacological study could be established through in vivo assays in order to discover new anticarcenogenic, anti-inflammatory, antimutagenic and other activities of M. spicata. Such results could be used in pharmaceutical formulations, leading to new human drugs from this medicinal plant.

This study assessed the anti-inflammatory effect of thiamine (TA) in lipopolysaccharide-stimulated RAW264.7 cells and also assessed the preservative properties of TA in minced beef. TA demonstrated a concentration-dependent antimicrobial effect on microbial contaminants. Inhibition zones and MIC from the effect of TA on the tested bacterial strains were respectively within the ranges 15–20 mm and 62.5–700 µg/mL. TA significantly (p < 0.05) decreased all the pro-inflammatory factors [(nitric oxide (NO), prostaglandin E2 (PGE2), TNF-α, IL-6, IL-1β, and nuclear factor-κB (NF-κB)] monitored relative to LPS-stimulated RAW264.7 cells. TA inhibited the expression of both iNOS and COX-2. In minced beef flesh, the growth of Listeria monocytogenes was inhibited by TA. TA improved physicochemical and microbiological parameters of stored minced beef meat compared to control. Principal component analyses and heat maps elucidate the quality of the tested meats.

Pelargonium graveolens essential oil was extracted from dried leaves by a clevenger apparatus and the composition of this essential oil was analyzed by GC-MS. The main results showed that P. graveolens essential oil was characterized by the predominance of two compounds: citronellol and geraniol with respective amounts of 27.53 and 25.85 %. In addition to that, P. graveolens essential oil was characterized by the predominance of oxygenated monoterpenes (70.64 %) which were followed by sesquiterpenes (11.88 %), acids (1.76 %) and hydrocarbon monoterpenes (2.02 %). Other compounds were detected with an amount of 11.83 %. Furthermore, the antioxidant activity of this volatile oil was assessed by DPPH test. We also tested its biological activity against some microorgnisms: Escherichia Coli (ATCC 25922), Staphylococcus aureus (ATCC 29213) and Bacillus subtilis (ATCC 6633) and also a fungi: Candida albicans (ATCC 10231). According to the results of DPPH test, The essential oil of P. graveolens was able to release free groups with a high capacity to oxidize free radicals of DPPH molecule. The antibacterial assay showed that P. graveolens essential oil was active against all the tested microorganisms with a more pronounced effect against Candida albicans and Bacillus subtilis.