Abstract
Cactus pear (Opuntia ficus-indica L.) is widely distributed in the arid and semi-arid regions throughout the world. In the last decades, the interest towards vegetative crop increased, and cladodes are exploited for nutraceutical and health-promoting properties. This study aimed at investigating the capacity of selected lactic acid bacteria to increase the antioxidant and anti-inflammatory properties of cactus cladodes pulp, with the perspective of producing a functional ingredient, dietary supplement or pharmaceutical preparation. Preliminarily, the antioxidant activity was determined through in vitro assays. Further, it was confirmed through ex vivo analysis on intestinal Caco-2/TC7 cells, and the profile of flavonoids was characterized. Cactus cladode pulp was fermented with lactic acid bacteria, which were previously selected from plant materials. Chemically acidified suspension, without bacterial inoculum and incubated under the same conditions, was used as the control. Lactobacillus plantarum CIL6, POM1 and 1MR20, Lactobacillus brevis POM2 and POM4, Lactobacillus rossiae 2LC8 and Pediococcus pentosaceus CILSWE5 were the best growing strains. Fermentation of cladode pulp with L. brevis POM2 and POM4 allowed the highest concentration of γ-amino butyric acid. Lactic acid fermentation had preservative effects (P<0.05) on the levels of vitamin C and carotenoids. Two flavonoid derivatives (kaemferol and isorhamnetin) were identified in the ethyl acetate extracts, which were considered to be the major compounds responsible for the increased radical scavenging activity. After inducing oxidative stress by IL-1β, the increased antioxidant activity (P<0.05) of fermented cladode pulp was confirmed using Caco-2/TC7 cells. Fermented cladode pulp had also immune-modulatory effects towards Caco-2 cells. Compared to the control, fermented cladode pulp exhibited a significantly (P<0.05) higher inhibition of IL-8, TNFα and prostaglandins PGE2 synthesis. The highest functional effect was found using ethyl acetate extracts. In conclusion, fermentation, especially with L. plantarum strains and L. brevis POM4, enhanced the antioxidant and immune-modulation features of cladode pulp.
Highlights
Cactus (Opuntia spp.), belonging to Cactaceae family, is cultivated in both hemispheres and all continents
13 strains of lactic acid bacteria, which were previously isolatedand identified from vegetables and fruits [15,16,17,18,19,20], and selected based on technology and functional features (Table 1), were assayed during single fermentation (30°C for 24 h) of cactus young cladode pulp (CP)
After 24 h, Lactobacillus fermentum F1 and Leuconostoc mesenteroides K16 were the only strains that did not grow on CP
Summary
Cactus (Opuntia spp.), belonging to Cactaceae family, is cultivated in both hemispheres and all continents. Because of the trend of Mediterranean area towards global desertification and decline of water resources, O. ficus-indica has an interesting potential as fruit and vegetative crop. The various vegetative parts of O. ficus-indica have marked economic importance, and are exploited as foods and pharmaceuticals [3]. Less valuable than fruit crops, the interest towards vegetative crop of O. ficus-indica increased in the last decades. O. ficus-indica was used in traditional folk medicine, and, recently, the popularity of cladodes increased in developed countries, being recognized as source of phytochemicals and prebiotics [6]. Cladode extracts were used for technological applications as dietary supplements, ingredients for beverages, breakfast cereals and margarine or thickening agents in vegetable soups and dessert gels [11, 12]. Cladode-gel exert a healing effect on dermal wounds [13]
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