Search Results (5)

Wounding stress stimulates secondary metabolism and induces the phytochemical accumulation of fresh-cut fruit and vegetables. This research aims to study the biosynthesis of secondary metabolites in citrus peel by-products after different wounding intensities. Orange, grapefruit, and lemon peels were cut into rectangular shapes of 8.5 × 2 cm (CTRL), 1 × 1 cm dices (D), and 0.25 cm grates (G). Samples were stored at 15 °C and 65% relative humidity. Their total phenolic content (TPC), total antioxidant capacity (TAC), and individual organic and phenolic compounds were analyzed after 0, 4, 8, 24, 28, and 36 h. The results showed that the metabolite content decreased with the incubation time, so it is recommended to sample by-products between the first 8 h to achieve the maximum content. Grating, the most severe abiotic stress, was not a suitable technique to induce the synthesis of biocompounds because it allowed the full recovery of flavedo, but partial of albedo. However, it was different for CTRL and D, whose TPCs were ~170 and ~200%, ~98 and ~78%, and ~8 and ~36% higher for orange, grapefruit, and lemon, respectively, compared to G. A principal component analysis confirmed differences between the fruit species and cutting shapes combining all factors. Wounding citrus peels induces the accumulation of phytochemical compounds, but the layer of peel recovered in the cut is crucial in the concentration of phytochemicals extracted. It could be an innovative tool to revalorize these inedible parts of citrus, but further research is still needed. Full article

Citrus fruits have been the subject of extensive research over the years due to their impressive antioxidant properties, the health benefits of flavanones, and their potential use in the prevention and treatment of chronic diseases. Grapefruit have been shown in studies to improve overall health, with numerous potential benefits, including improved heart health, reduced risk of certain cancers, improved digestive health, and improved immune system function. The development of cyclodextrin complexes is an exciting approach to increasing the content of flavanones such as naringin and naringenin in the extraction medium while improving the profile of beneficial phenolic compounds and the antioxidant profile. This research aims to optimize the extraction conditions of the flavanones naringin and naringenin with additional compounds to increase their yield from different parts of grapefruit (Citrus × paradisi L.) fruits, such as albedo and segmental membranes. In addition, the total content of phenolic compounds, flavonoids, and the antioxidant activity of ethanolic extracts produced conventionally and with -cyclodextrin was examined and compared. In addition, antioxidant activity was measured using the radical scavenging activity assay (ABTS), radical scavenging activity assay (DPPH), and ferric reducing antioxidant power (FRAP) methods. The yield of naringin increased from 10.53 ± 0.52 mg/g to 45.56 ± 5.06 mg/g to 51.11 ± 7.63 mg/g of the segmental membrane when cyclodextrins (α, β-CD) were used; naringenin increased from 65.85 ± 10.96 μg/g to 91.19 ± 15.19 μg/g of the segmental membrane when cyclodextrins (α, β-CD) were used. Furthermore, the results showed that cyclodextrin-assisted extraction had a significant impact in significantly increasing the yield of flavanones from grapefruit. In addition, the process was more efficient and less expensive, resulting in higher yields of flavanones with a lower concentration of ethanol and effort. This shows that cyclodextrin-assisted extraction is an excellent method for extracting valuable compounds from grapefruit. Full article

This study aimed to develop a method of naringinase biosynthesis by Aspergillus niger KMS on an optimized culture medium. The concentration of the six medium components in shake flasks was optimized by the Box and Wilson factor gradient method. Naringinase’s substrate, naringin, powdered albedo, flavedo, and red grapefruit segment membranes were used to stimulate naringinase biosynthesis. Rhamnose was chosen as the carbon source, while the nitrogen source was yeast extract and sodium nitrate. Naringinase biosynthesis was most favorable in the culture medium with the following composition (g 100 mL): 3.332—NaNO₃; 3.427—yeast extract; 0.184—KH₂PO₄; 0.855—red grapefruit albedo; 0.168—naringin; 2.789—rhamnose. The obtained Aspergillus niger KMS culture fluid was concentrated, thereby precipitating the protein. As a result, a naringinase preparation with high activity, equal to 816 µmol × min⁻¹ × g⁻¹, was obtained. Full article

While flavanones exist in a variety of chemical forms, their favorable health effects are most prominent in their free form—aglycones. Their concentrations in grapefruit (Citrus × paradisi L.) extracts vary according to the extraction and hydrolysis methods used. The primary aim of this work was to maximize the yields of naringin and naringenin from various parts of fresh grapefruit fruits (flavedo, albedo, and segmental) using different extraction and hydrolysis methods. In addition, we aimed to evaluate the excipient—magnesium aluminometasilicate—and determine its influence on the qualitative composition of grapefruit extracts. Extracts were obtained by heat reflux extraction (HRE), ultrasound-assisted extraction with an ultrasonic homogenizer (UAE*), and ultrasound-assisted extraction with a bath (UAE). Ultrasound-assisted extraction using a bath (UAE) was modulated using acidic, thermal, and alkaline hydrolysis. The highest yield of naringin 8A (17.45 ± 0.872 mg/g) was obtained from an albedo sample under optimal conditions using ultrasound-assisted extraction; a high yield of naringenin 23-SHR (35.80 ± 1.79 µg/g) was produced using the heat reflux method from the segmental part. Meanwhile, ultrasonic combined with thermal hydrolysis significantly increased flavanone extraction from the albedo and segmental parts: naringin from sample 9-A (from 17.45 ± 0.872 mg/g to 25.05 ± 1.25 mg/g) and naringenin from sample 15-S (from 0 to 4.21 ± 0.55 µg/g). Additionally, magnesium aluminometasilicate demonstrated significant increases of naringenin from all treated grapefruit parts. To our knowledge, this is the first report of magnesium aluminometasilicate used as an adsorbent in flavanone extractions. Full article

Flavor traits in citrus are the result of a blend of low molecular weight metabolites including sugars, acids, flavonoids and limonoids, these latter being mainly responsible for the characteristic bitter flavor in citrus. In this work, the genotype- and developmental stage-dependent accumulation of flavonoids and limonoids is addressed. To fulfill this goal, three models for citrus bitterness: bitter Duncan grapefruit, bittersweet Thomson orange and sweet Wase mandarin were selected from a total of eight different varieties. Compounds were annotated from LC/ESI-QqTOF-MS non-targeted metabolite profiles from albedo and pulp tissues. Results indicated that the specific blend of compounds providing the characteristic flavor trait is genotype-specific and hence under genetic control, but it is also regulated at the developmental level. Metabolite profiles in albedo mirrored those found in pulp, the edible part of the fruit, despite differences in the concentration and accumulation/depletion rates being found. This is particularly relevant for polymethoxylated flavones and glycosylated limonoids that showed a clear partitioning towards albedo and pulp tissues, respectively. Fruit ripening was characterized by a reduction in flavonoids and the accumulation of limonoid glycosides. However, bitter grapefruit showed higher levels of limonin A-ring lactone and naringin in contrast to sweeter orange and mandarin. Data indicated that the accumulation profile was compound class-specific and conserved among the studied varieties despite differing in the respective accumulation and/or depletion rate, leading to different specialized metabolite concentration at the full ripe stage, consistent with the flavor trait output. Full article