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In the present study, betalains content, phenolic composition, and antioxidant activity of different parts of red beet (Beta vulgaris L. conditiva) (i.e., roots and stems) were compared. Crude extract of root showed the highest betalain content with a maximum of 53 ± 4 mg betanin eq and 46 ± 3 mg vulgaxantin I eq g −1 of extract stems showed higher total phenolic concentration than roots, ranging between 2.0 ± 0.4 and 14.6 ± 0.5 mg gallic acid eq −1 of extract. Chemical composition was analyzed using LC-MS. Betalains (vulgaxanthin I, betanin, and isobetanin) and phenolics (gallic acid, ferulic acid, chlorogenic acid, caffeic acid, vanillic acid, syringic acid, ellagic acid myricetin, quercetin, rutin, kampferol) were identified in roots and stems. Betalain extract obtained from roots showed higher antioxidant activity than extract obtained from stems.

In this study, different drying methodologies (convective air, oven and microwave) of Myrtus communis L. (M. communis L.) leaves were conducted to investigate their effects on the levels of phenolic compounds, antioxidant capacity of ethanolic extracts (EEs) as well as the soybean oil oxidative stability. Drying methodology significantly influenced the extractability of phenolic compounds. Microwave drying led to an increase in the amounts of total phenols, flavonoids and proanthocyanidins followed by oven drying at 70 °C. Higher temperature of drying (100 and 120 °C) led to a significant reduction of their amounts (p < 0.05). An ultra-performance liquid chromatography method combined with high resolution mass spectroscopic detection was used to analyze the phenolic fraction of extracts. Higher amounts of the identified compounds were observed when leaves were heat treated. Furthermore, the evaluation of the antioxidant activity showed that the studied extracts possess in general high antioxidant capacities, significantly dependent on the employed drying methodology. The incorporation of the different extracts at 200 ppm in soybean oil showed that its oxidative stability was significantly improved. Extracts from leaves treated with microwave (EE_MW) and at 70 °C (EE_70) have better effect than BHT. The results of the present study suggest that microwave drying could be useful to enhance the extractability of phenolic compounds and the antioxidant capacity of M. communis L. leaf extract.

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International audiencePurpose - The paper aims to analyse the effect of acid hydrolysis on the chemical composition and the biological activities of Rubia tinctorum collected from the south of Tunisia. It proposes to clarify the relationship between alizarin content and the antioxidant and antimicrobial activities of Rubia extract.Design/methodology/approach - The paper opted for analytical tools (HPLC) and the in-vitro study of biological activities, namely, the antioxidant activity which is evaluated using the radical scavenging assay (ABTS) and ferric reducing power assay (FRAP); the antimicrobial activity is tested using the wells agar diffusion method.Findings - The paper provides information about the positive effect of acid hydrolysis, namely, the enhancement of alizarin content in the extract which has increased its antioxidant and antimicrobial activities.Originality/value - This paper fulfils an identified need to study the relationship between the chemical composition, biological activities and colour enhancement