By-products of Opuntia ficus-indica as a source of antioxidant dietary fiber

Dietary fiber and bioactive compounds are widely used as functional ingredients in processed foods. The market in this field is competitive and the development of new types of quality ingredients for the food industry is on the rise. Opuntia ficus-indica (cactus pear) produces edible tender stems (cladodes) and fruits with a high nutritional value in terms of minerals, protein, dietary fiber and phytochemicals; however, around 20% of fresh weight of cladodes and 45% of fresh weight of fruits are by-products. The objective of this study was therefore to determine the nutritional value of by-products obtained from cladodes and fruits from two varieties of Opuntia ficus-indica, examining their dietary fiber and natural antioxidant compound contents in order to obtain quality ingredients for functional foods and increase the added value of these by-products.

Bioactive compounds of four hot pepper varieties (Capsicum annuum L.), antioxidant capacity, and intestinal bioaccessibility

Pepper fruits (Capsicum annuum) contain a wide array of phytochemicals with well-known antioxidant properties. Since bioactive compounds depend on their bioavailability to exert beneficial effects, it was crucial to estimate the extent of release from the food matrix and thus their bioaccessibility. Accordingly, we determined the individual carotenoid and phenolic content as well as the antioxidant properties of four red hot dried cultivars (Capsicum annuum L.) of high consumption in Mexico and estimated the extent of intestinal bioaccessibility of carotenoids with significance in human health, beta-carotene, beta-cryptoxanthin, and zeaxanthin, using an in vitro gastrointestinal model. Hot dried peppers at ripe stage had a high content of bioactive compounds that exhibited significant antioxidant properties (26-80 micromol trolox equivalents/g of dry matter), such as polyphenols (>2000 mg/100 g of dry matter) and carotenoids (95-437 mg/100 g of dry matter), which were partially bioaccessible. The amount released from the food matrix by the action of digestive enzymes was about 75% for total polyphenols, up to 49% for both beta-carotene and zeaxanthin, and up to 41% for beta-cryptoxanthin. The results suggest that from 50 to 80% of these carotenoids could reach the colon to be potentially fermented or could remain unavailable.

Inactivation of betaine aldehyde dehydrogenase from Pseudomonas aeruginosa and Amaranthus hypochondriacus L. leaves by disulfiram

Betaine aldehyde dehydrogenase (BADH) activity might be crucial for the growth of the human pathogen Pseudomonas aeruginosa under conditions of infection and therefore appears to be a suitable target for antimicrobial agents. As a first step in the search for BADH inhibitors, we have tested the effects of the known aldehyde dehydrogenase inhibitor disulfiram (DSF) on the activity of P. aeruginosa and Amaranthus hypochondriacus (amaranth) leaf BADHs. DSF totally inactivated both enzymes in a time- and dose-dependent manner. In the case of the Pseudomonas enzyme, inactivation kinetics were monophasic with a second-order inactivation rate constant at pH 6.9 of 4.9+/-0.4 M(-1) s(-1), whereas the plant enzyme was inactivated in a biphasic process with second-order inactivation rate constants at pH 7.5 of 6.8+/-0.6 and 0.33+/-0.04 M(-1) s(-1). At pH 8.8, the second-order rate constants for inactivation of the bacterial enzyme was 1 x 10(3) M(-1) s(-1), which compare well with that reported for human liver mitochondrial aldehyde dehydrogenase (ALDH2), the target of DSF inhibition in the aversion therapy of alcoholism. Both BADHs were inactivated faster in the presence of NAD(P)(+) than in its absence, whereas NAD(P)H and betaine aldehyde protected the bacterial, but increased the inactivation rate of the plant enzyme. The inactivated enzymes were reactivated by dithiothreitol, but not by a high concentration of the physiological reductant glutathione. The high in vitro sensitivity of the Pseudomonas BADH to DSF, particularly in the presence of NAD(P)(+), together with the lack of reversibility of DSF modification by glutathione, makes this inhibitor a potential antimicrobial agent and suggests that it might be worth testing its effects and those of its metabolites in vivo, under culture conditions in which the activity of BADH is required for growth of the bacteria.