Phenolic compounds profile of water and ethanol extracts of Euphorbia hirta L. leaves showing antioxidant and antifungal properties

The bioactive chemical constituents of water and ethanol extracts of Euphorbia hirta L. leaves have been identified and quantified using an un-targeted mass spectrometric approach. The study allowed the tentative identification of 123 individual phenolic compounds and 18 non-phenolic phytochemicals, most of them described in Euphorbia hirta L. leaves for the first time. Gallotannins, hydroxybenzoic and hydroxycinnamic acids were the most abundant phenolic classes in Euphorbia hirta L. leaves, representing together the 71.5% (26.3%, 25.2% and 20%, respectively) of the total amount of identified phenolics. The main phenolic compounds detected were tri-O-galloyl-glucose isomers, feruloyl-coniferin, tetra-O-galloyl-glucose isomers, di-O-galloyl-glucose isomers, ethyl-gallic acid, protocatechuic acid-O-pentoside-O-hexoside, 5-O-caffeoyl-quinic acid trans isomer and digalloyl-quinic acid. Feruloyl-coniferin was found to be approximately six times more concentrated in the ethanol extract with respect to the water extract. The ethanol extract exhibited higher ABTS (1338.3 ± 85.3 and 802.3 ± 91.0 μmol ascorbic acid equivalent/gram of dry extract, respectively) and superoxide anion (2014.6 ± 78.6 and 1528.0 ± 111.7 μmol ascorbic acid equivalent/gram of dry extract, respectively) scavenging abilities than the water extract. Additionally, the ethanol extract also showed a remarkable anti-fungal effect against Fusarium oxysporum f. sp. vasinfectum, Alternaria solani and Rhizoctonia solani. This study provides new information about Euphorbia hirta L., offering reasons to promote this plant species as rich source of phenolics and an excellent source of antifungal molecules that might have a prospective use in controlling fungal diseases of vegetable crops

Activity of extracts from three tropical plants towards fungi pathogenic to tomato (Solanum lycopersicum)

Antifungal properties were assessed of water and ethanol extracts from the pan-tropical plants Oxalis barrelieri L., Stachytarpheta cayennensis L., and Euphorbia hirta L. against Fusarium oxysporum f. sp. vasinfectum, Alternaria solani Sorauer, and Rhizoctonia solani Kuhn. The plant extracts inhibited fungal growth in vitro at 1.25-20 mg mL-1, and the degrees of inhibition increased in a dose-dependent manner. Ethanol extracts from the plants inhibited fungal growth by 80-100%, while water extracts showed less antifungal activity, with maximum growth inhibition of 62%. Growth inhibition from ethanol extracts was two- to three-fold greater than for water extracts at equivalent concentrations. Antifungal activity of the extracts varied with their content and composition of phenolics, flavonoids, tannins, and alkaloids. In greenhouse experiments, spraying tomato plants (Solanum lycopersicum L.) with ethanol extract from E. hirta at 2.5 mg mL-1 did not cause phytotoxicity, and increased plant size, when compared to untreated plants. Spraying E. hirta ethanol extract on tomato plants infected by R. solani reduced disease severity up to 80%, when compared to non-sprayed plants. These results demonstrate potential of leaf extracts from E. hirta, O. barrelieri, and S. cayennensis as biofungicides for the control of R. solani, A. solani, and F. oxysporum, which are among the most important causal agents of tomato diseases

ANTIFUNGAL ACTIVITY OF AQUEOUS AND ETHANOL EXTRACTS OF TROPICAL PLANTS AGAINST TOMATO FUNGAL PATHOGENES.

Several plant extracts may have a strong antifungal activity that can be exploited in the management of fungal diseases as an alternative to synthetic fungicides, the abuse of which may have consequences on the environment and health. Ethanol extracts (EE) and water extracts (WE) of three tropical plants, Stachytarpheta cayennensis (Verbenaceae), Oxalis barrelieri (Oxalidaceae) and Euphorbia hirta (Euphorbiaceae) were obtained and screened for their antifungal activity against three major phytopathogenic fungi of tomato: Fusarium sp., Alternaria sp. and Colletotrichum sp. The phytopathogenic fungi used across the experiments were isolated in Cameroon on severely affected tomatoes and their molecular identification and characterization is ongoing. The antifungal activity was checked in vitro on different media supplemented with different concentrations of the extracts. O. barrelieri EE, at the concentration of 25 mg/ml, inhibited the mycelium growth of Fusarium sp. by 26.8% and remarkably modified its morphology. WE and EE of the same O. barrelieri inhibited the mycelium growth of Colletotrichum sp. by 43.7% and 50.3% respectively, but showed no inhibition on Alternaria sp. The phytochemical analysis of these plant extracts revealed that EE of S. cayennensis was the richest in polyphenols and flavonoids. EE from O. barrelieri was particularly rich in alkaloids. The inhibitory effects on the phytopathogenic fungi were possibly related to the amount of polyphenols and alkaloids obtained through the extraction. Field experiments are being conducted on tomato to confirm the action of such extracts in vivo. These findings may contribute to develop new biofungicides to protect tomato from some fungal pathogens