Exploring the chemical composition and biological activity of different fruit varieties is essential for the valorization of their health claims. The current study focuses on a detailed comparative analysis of three early- and two mid-ripening peach varieties: “Filina” (peach), “July Lady” (peach), “Laskava” (peach), “Gergana” (nectarine), and “Ufo 4” (flat peach). They were characterized in terms of essential nutrients such as carbohydrates (sugars and dietary fibers), amino acid content, and lipids as well as mineral content, fat-soluble vitamins, carotenoids, and chlorophyll. Polyphenolic compounds and the related antioxidant activity were also assessed. The methanolic extract of the peel seems to be richer in the studied biologically active substances compared to the fleshy part of the fruit. Anthocyanins were most abundant in “Gergana” and “July Lady” extracts (6624.8 ± 404.9 and 7133.6 ± 388.8 µg cyanidin-3-glucoside/100 g fw, resp.). The total phenol content of the samples varied from 34.11 ± 0.54 to 157.97 ± 0.67 mg gallic acid equivalents (GAE)/100 g fw. “Filina” and “July Lady” varieties possessed the highest antioxidant activity. Overall, the results of this study confirm that the studied peach varieties have satisfactory nutritional value and are potential sources of biologically active substances. Each variety represents an individual palette of nutrients that should be considered separately from the other.

Fruits contain a number of useful substances including antioxidants. Their bio-accessibility after passing through the digestive tract is of primary importance when considering their benefits. In this respect, we investigated the effect of in vitro digestion on the phytochemicals of eight fruit juices. Freshly prepared juices from pomegranate, orange and grapefruit were used as well as commercially available juices from cherry, black grapes and aloe vera, blackberry and chokeberry, and two types of chokeberry and raspberries. Spectrophotometric and HPLC methods were used in order to analyse the sugar content, the total phenolic (TPC) and flavonoid contents (TFC), anthocyanins, phenolic acids and antioxidant activity. Principle component analysis was used to explain the differentiation among the types of fruit juice. Sugar recovery variation was between 4–41%. The bio-accessibility of TPC ranged from 13.52–26.49% and of flavonoids between 24.25–67.00%. The pomegranate juice and the juice of black grapes and aloe vera kept 58.12 and 50.36% of their initial anthocyanins content, while for the other samples less than 1.10% was established. As a result, a maximum of 30% remaining antioxidant activity was measured for some of the samples, but for most this was less than 10%. In conclusion, fruit juices are a rich source of biologically active substances, but a more detailed analysis of food transformation during digestion is needed.

Beetroot, the cultivated form of Beta vulgaris subsp. vulgaris, is known for its various beneficial properties but more critical data about its bioactive compounds digestion is needed. In the present research, the bioaccessibility of phytochemicals in freshly prepared red beetroot juice was...

Members of the bacterial genus Bacillus are known as producers of a broad spectrum of antibiotic compounds of proteinaceous nature that possess inhibitory activity against different saprophytic and pathogenic microorganisms. In the current research, a peptide synthesized by Bacillus methylotrophicus strain BM47, previously isolated from a natural thermal spring in Bulgaria, was identified and characterized as a bacteriocin. In vitro antimicrobial screening of the crude bacteriocin substance of B. methylotrophicus BM47 showed activity against the plant pathogenic fungi Fusarium moniliforme, Aspergillus awamori, Penicillium sp., Aspergillus niger and Gram-negative bacterium Pseudomonas aeruginosa. The antimicrobial activity of the crude bacteriocin substance was partially inhibited by the enzymes trypsin, Alcalase®, Savinase®, proteinase K, papain and Esperase®, while catalase was not effective. The crude bacteriocin substance was relatively pH resistant, but sensitive to the action of heat and most organic solvents and detergents tested. To obtain the active protein fractions, crude bacteriocin substance was purified by fast protein liquid chromatography (FPLC) using a strong anion exchange column. Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis demonstrated that the purified bacteriocin had molecular mass of 19 578 Da. The amino acid analysis performed by high-performance liquid chromatography (HPLC) revealed that the isolated bacteriocin consisted of 17 types of amino acids, with the highest mol fraction expressed as percent of serine (29.3), valine (10.3), alanine (9.8) and tyrosine (7.1).

The solubility of plant protein isolates is a key determinant of their potential application. Two protein isolates (PI) from ethanol-treated industrial rapeseed meal, PI_10.5–2.5 and PI_2.5–8.5, were prepared by sequential isoelectric precipitation of alkali-extracted proteins (pH 12) starting from pH 10.5 to 2.5 or from pH 2.5 to 8.5, respectively. Biochemical analyses revealed that PI_2.5–8.5 contained a higher amount of crude protein (72.84%) than PI_10.5–2.5 (68.67%). In the same protein isolate, the level of total phenols (0.71%) was almost two-fold higher than that in PI_10.5–2.5 (0.42%). No glucosinolates were established in both protein isolates. SDS-PAGE analysis demonstrated that PI_10.5–2.5 contained 10 to 15 kDa protein fractions in a relatively higher amount, while PI_2.5–8.5 was enriched in 18 to 29 kDa protein fractions. PI_10.5–2.5 exhibited high solubility, varying from 41.74% at pH 4.5 to 65.13% at pH 6.5, while PI_2.5–8.5 was almost two-fold less soluble under the same conditions. Up to pH 5.5, the addition of NaCl at 0.03 and 0.25 M diminished the solubility of PI_2.5–8.5, while the solubility of PI_10.5–2.5 was increased. The supplementation of PI_10.5–2.5 with 0.25 M NaCl enhanced the protein solubility to 56.11% at pH 4.5 and 94.26% at pH 6.5. The addition of 0.03 M NaCl also increased the solubility of this protein isolate but to a lower extent. Overall, the approach for sequential precipitation of proteins influenced the biochemical characteristics, protein fractional profile and solubility of prepared protein isolates.

The inhibition of certain digestive enzymes by target food matrices represents a new approach in the treatment of socially significant diseases. Proving the ability of fruits to inhibit such enzymes can support the inclusion of specific varieties in the daily diets of patients with diabetes, obesity, Alzheimer’s disease, etc., providing them with much more than just valuable micro- and macromolecules. The current study aimed atidentifying and comparing the GC-MS metabolic profiles of eight peach varieties (“Filina”, “Ufo 4, “Gergana”, “Laskava”, “July Lady”, “Flat Queen”, “Evmolpiya”, and “Morsiani 90”) grown in Bulgaria (local and introduced) and to evaluate the inhibitory potential of their extracts towards α-glucosidase, α-amylase, lipase, and acetylcholinesterase. In order to confirm samples’ differences or similarities, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were also applied to the identified metabolites. The results provide important insights into the metabolomic profiles of the eight peach varieties and represent a first attempt to characterize the peels of the peach varieties with respect to α-glucosidase-, α-amylase-, lipase-, and acetylcholinesterase-inhibitory activities. All of the studied peach extracts displayed inhibitory activity towards α-glucosidase (IC₅₀: 125–757 mg/mL) and acetylcholinesterase (IC₅₀: 60–739 mg/mL), but none of them affected α-amylase activity. Five of the eight varieties showed inhibitory activity towards porcine pancreatic lipase (IC₅₀: 24–167 mg/mL). The obtained results validate the usefulness of peaches and nectarines as valuable sources of natural agents beneficial for human health, although further detailed investigation should be performed in order to thoroughly identify the enzyme inhibitors responsible for each activity.