In vitrodigestibility of phenolic compounds from edible fruits: could it be explained by chemometrics?

Identification of key phenolic compounds responsible for antioxidant activities of free and bound fractions of blackberry varieties' extracts by boosted regression trees

BACKGROUND

Free fractions of different blackberry varieties' extracts are high in phenolic compounds with antioxidant activities. However, the phenolic profiles and antioxidant activities against peroxyl radicals of bound fractions of different blackberry varieties' extracts have not been previously reported. In addition, what the key antioxidant phenolic compounds are in free and bound fractions of blackberry extracts remain unknown. This study aimed to investigate the phenolic profiles and antioxidant activities of free and bound fractions of eight blackberry varieties' extracts and reveal the key antioxidant phenolic compounds by boosted regression trees.

RESULTS

Fifteen phenolics (three anthocyanins, four flavonols, three phenolic acids, two proanthocyanidins, and three ellagitannins) were identified in blackberry by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Ferulic acid, ellagic acid, procyanidin C1, kaempferol-O-hexoside, ellagitannins hex, and gallic acid were major bound phenolics. Bound fractions of eight blackberry varieties' extracts were high in phenolics and showed great antioxidant activity. Boosted regression trees analysis showed that cyanidin-3-O-glucoside and chlorogenic acid were the most significant compounds, contributing 48.4% and 15.9% respectively to the antioxidant activity of free fraction. Ferulic acid was the most significant antioxidant compound in bound fraction, with a contribution of 61.5%. Principal component analysis showed that Kiowa was the best among the eight varieties due to its phenolic profile and antioxidant activity.

CONCLUSION

It was concluded that blackberry varieties contained high amounts of bound phenolics, which confer health benefits through reducing oxidative stress. Ferulic acid was the key compound to explain the antioxidant activities of bound fractions. © 2021 Society of Chemical Industry.

Sensory attributes, physicochemical and antioxidant characteristics, and protein profile of wild prickly pear fruits (O. macrocentra Engelm., O. phaeacantha Engelm., and O. engelmannii Salm-Dyck ex Engelmann.) and commercial prickly pear fruits (O. ficus-indica (L.) Mill.)

Mexico presents the highest richness of Opuntia Mill. species. These species are an important economic factor for the country, and source of nutrients, bioactive compounds, pigments, and nutraceuticals which can be of interest for the food and pharmaceutical industry. However, there are some wild Opuntia species in the Chihuahua desert, that have not been analyzed to establish their properties and potential use. The aim of study was to evaluate the sensory, physicochemical and protein profile in wild prickly pear fruits (O. macrocentra Engelm. (OM), O. phaeacantha Engelm. (OP), and O. engelmannii Salm-Dyck ex Engelmann. (OE)) from Samalayuca, Chihuahua and compare them with two commercial prickly pear fruits (O. ficus-indica (L.) Mill. (green-OFG, red-OFR). The sensory profile of wild species was characterized by highest color, odor, and sour taste compared to the commercial fruits. Pulp, peel, and seeds from wild prickly pear fruits showed lower pH, and higher titratable total acidity, total phenolic compounds, total flavonoids, antioxidant capacity, protein, lipids, ash, carbohydrates (only peel), and crude fiber content than commercial Opuntia species. Furthermore, O. engelmannii showed a tendency to present the highest betacyanins, betaxanthins, and betalains contents. A total of 181, 122, 113, 183 and 140 different proteins were identified in OM, OP, OE, OFG, OFR species, respectively. All species showed the highest enrichment in three main pathways such as amino acids biosynthesis, glycolysis (dark)/gluconeogenesis (light), and the citric acid cycle. The wild prickly pear fruits of this study showed important nutritional, protein, and antioxidant properties with biological interest, and can be a potential source of functional ingredients and nutraceuticals.

First-Pass Metabolism of Polyphenols from Selected Berries: A High-Throughput Bioanalytical Approach

Small berries are rich in polyphenols whose first-pass metabolism may alter their ultimate physiological effects. The antioxidant capacity and polyphenol profile of three freeze-dried berries (blackberry, raspberry, Red Globe grape) were measured and their apparent permeability (Papp) and first-pass biotransformation were tracked with an ex vivo bioanalytical system [everted gut sac (rat) + three detection methods: spectrophotometry, HPLC-ESI-QTOF-MS, differential pulse voltammetry (DPV)]. Total polyphenol (ratio 0.07-0.14-1.0) and molecular diversity (anthocyanins>flavan-3-ols), antioxidant capacity (DPPH, FRAP), anodic current maxima and Papp (efflux> uptake) were in the following order: blackberry > raspberry > Red Globe grape. Epicatechin, pelargonidin & cyanin (all), callistephin (raspberry/blackberry), catechin (grape), cyanidin glycosides (blackberry) and their derived metabolites [quinic acid, epicatechin, cyanidin/malvidin glucosides, and chlorogenic/caffeic acids] were fruit-specific and concentration-dependent. Time-trend DPV kinetic data revealed concurrent epithelial permeability & biotransformation processes. Regular permeability and high-biotransformation of berry polyphenols suggest fruit-specific health effects apparently at the intestinal level.

Chemical Composition and In Vitro Bioaccessibility of Antioxidant Phytochemicals from Selected Edible Nuts

The ultimate health benefits of peanuts and tree nuts partially depend on the effective gastrointestinal delivery of their phytochemicals. The chemical composition and in vitro bioaccessibility of tocopherols, tocotrienols and phenolic compounds from peanuts and seven tree nuts were evaluated by analytical and chemometric methods. Total fat and dietary fiber (g 100 g-1) ranged from 34.2 (Emory oak acorn) to 72.5 (pink pine nut; PPN) and from 1.2 (PPN) to 22.5 (pistachio). Samples were rich in oleic and linoleic acids (56-87 g 100 g-1 oil). Tocopherols and tocotrienols (mg·kg-1) ranged from 48.1 (peanut) to 156.3 (almond) and 0 (almond, pecan) to 22.1 (PPN) and hydrophilic phenolics from 533 (PPN) to 12,896 (Emory oak acorn); flavonoids and condensed tannins (mg CE.100 g-1) ranged from 142 (white pine nut) to 1833 (Emory oak acorn) and 14 (PPN) to 460 (Emory oak acorn). Three principal components explained 90% of the variance associated with the diversity of antioxidant phytochemicals in samples. In vitro bioaccessibility of tocopherols, tocotrienols, hydrophilic phenolics, flavonoids, and condensed tannins ranged from 11-51%, 16-79%, 25-55%, 0-100%, and 0-94%, respectively. Multiple regression analyses revealed a potential influence of dietary fiber, fats and/or unsaturated fatty acids on phytochemical bioaccessibility, in a structure-specific manner.