Eighty-eight extracts of different polarity obtained from 18 Lamiaceae medicinal and aromatic plants were screened for their antioxidant and antifungal properties. A TLC analysis combined with two bioassays were used to detect these activities. In most cases the highest radical scavenger capacity was detected in methanolic and aqueous extracts and polyphenols may be responsible. The most interesting antioxidant activity was observed in polar extracts obtained from Lycopus europaeus, Melissa officinalis, Origanum vulgare subsp. virens and Lavandula latifolia. On the contrary, the best results for the antifungal test against Rhizopus stolonifer were produced by non-polar herbal extracts. Phlomis lychnitis, Salvia pratensis and Calamintha sylvatica caused the highest inhibition on Rhizopus growth.

The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface.

The scavenging activity against DPPH (1,1-diphenil-2-picrylhydrazyl) radical and the antifungal effect against chloroform, ethyl acetate and 50% methanolic extracts of Verbena officinalis leaves were investigated. The activity of different fractions of 50% methanolic extract and some isolated compounds were also investigated. The results suggest that 50% methanolic extract and caffeoyl derivatives could potentially be considered as excellent and readily available sources of natural antifungal and antioxidant compounds.

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Dichloromethane, ethyl acetate, methanol, and aqueous extracts obtained from 16 Spanish medicinal plants were screened for their antioxidant and antifungal activities. The radical scavenging capacity was evaluated by the DPPH method using a rapid screening by TLC and a spectrophotometric assay. Polar extracts obtained from Jasonia gluti-, and Lythrum salicaria L. (Lythraceae) showed high antioxidant properties. Among them, the methanol extract of Lythrum salicaria showed the strongest antiradical capacity with an IC 50 value similar to the positive control ascorbic acid. On the contrary, the best antifungal properties against Rhizopus stolonifer were produced by ethyl acetate or dichloromethane extracts from Anthemis arvensis L. subsp. arvensis (Asteraceae), Tanacetum parthenium, Santolina chamaecyparissus L. subsp. squarrosa Nyman (Asteraceae), Anagallis arvensis L. (Primulaceae) and the methanol extract of Anagallis foemina Miller (Primulaceae). The dichloromethane extract of Anthemis arvensis subsp. arvensis was the best inhibitor of fungus growth.