Saponins are steroid or triterpenoid glycosides, common in a large number of plants and plant products that are important in human and animal nutrition. Several biological effects have been ascribed to saponins. Extensive research has been carried out into the membrane-permeabilising, immunostimulant, hypocholesterolaemic and anticarcinogenic properties of saponins and they have also been found to significantly affect growth, feed intake and reproduction in animals. These structurally diverse compounds have also been observed to kill protozoans and molluscs, to be antioxidants, to impair the digestion of protein and the uptake of vitamins and minerals in the gut, to cause hypoglycaemia, and to act as antifungal and antiviral agents. These compounds can thus affect animals in a host of different ways both positive and negative.

Fig fruit has been a typical component in the health-promoting Mediterranean diet for millennia. To study the potential health-promoting constituents of fig fruits, six commercial fig varieties differing in color (black, red, yellow, and green) were analyzed for total polyphenols, total flavonoids, antioxidant capacity, and amount and profile of anthocyanins. Using reversed-phase liquid chromatography (RP-LC), various concentrations of anthocyanins but a similar profile was found in all varieties studied. Hydrolysis revealed cyanidin as the major aglycon. Proton and carbon NMR confirmed cyanidin-3-O-rhamnoglucoside (cyanidin-3-O-rutinoside; C3R) as the main anthocyanin in all fruits. Color appearance of fig extract correlated well with total polyphenols, flavonoids, anthocyanins, and antioxidant capacity. Extracts of darker varieties showed higher contents of phytochemicals compared to lighter colored varieties. Fruit skins contributed most of the above phytochemicals and antioxidant activity compared to the fruit pulp. Antioxidant capacity correlated well with the amounts of polyphenols and anthocyanins (R2 = 0.985 and 0.992, respectively). In the dark-colored Mission and the red Brown-Turkey varieties, the anthocyanin fraction contributed 36 and 28% of the total antioxidant capacity, respectively. C3R contributed 92% of the total antioxidant capacity of the anthocyanin fraction. Fruits of the Mission variety contained the highest levels of polyphenols, flavonoids, and anthocyanins and exhibited the highest antioxidant capacity.

Most studies on the reduction of disease incidence in soil treated with Trichoderma asperellum have focused on microbial interactions rather than on plant responses. This study presents conclusive evidence for the induction of a systemic response against angular leaf spot of cucumber (Pseudomonas syringae pv. lachrymans) following application of T. asperellum to the root system. To ascertain that T. asperellum was the only microorganism present in the root milieu, plants were grown in an aseptic hydroponic growth system. Disease symptoms were reduced by as much as 80%, corresponding to a reduction of 2 orders of magnitude in bacterial cell densities in leaves of plants pretreated with T. asperellum. As revealed by electron microscopy, bacterial cell proliferation in these plants was halted. The protection afforded by the biocontrol agent was associated with the accumulation of mRNA of two defense genes: the phenylpropanoid pathway gene encoding phenylalanine ammonia lyase (PAL) and the lipoxygenase pathway gene encoding hydroxyperoxide lyase (HPL). This was further supported by the accumulation of secondary metabolites of a phenolic nature that showed an increase of up to sixfold in inhibition capacity of bacterial growth in vitro. The bulk of the antimicrobial activity was found in the acid-hydrolyzed extract containing the phenolics in their aglycone form. High-performance liquid chromatography analysis of phenolic compounds showed a marked change in their profile in the challenged, preelicited plants relative to that in challenged controls. The results suggest that similar to beneficial rhizobacteria, T. asperellum may activate separate metabolic pathways in cucumber that are involved in plant signaling and biosynthesis, eventually leading to the systemic accumulation of phytoalexins.