Rambutan (Nephelium lappaceum L.) is a tropical fruit from Asia which has become the main target of many studies involving polyphenolic analysis. Mexico produces over 8 million tons per year of rambutan, generating a huge amount of agro-industrial waste since only the pulp is used and the peel, which comprises around 45% of the fruit’s weight, is left behind. This waste can later be used in the recovery of polyphenolic fractions. In this work, emerging technologies such as microwave, ultrasound, and the hybridization of both were tested in the extraction of phenolic compounds from Mexican rambutan peel. The results show that the hybrid technology extraction yielded the highest polyphenolic content (176.38 mg GAE/g of dry rambutan peel). The HPLC/MS/ESI analysis revealed three majoritarian compounds: geraniin, corilagin, and ellagic acid. These compounds explain the excellent results for the biological assays, namely antioxidant activity evaluated by the DPPH, ABTS, and LOI (Lipid oxidation inhibition) assays that exhibited great antioxidant capacity with IC₅₀ values of 0.098, 0.335, and 0.034 mg/mL respectively, as well as prebiotic activity demonstrated by a µMax (maximum growth) of 0.203 for Lactobacillus paracasei. Lastly, these compounds have shown no hemolytic activity, opening the door for the elaboration of different products in the food, cosmetic, and pharmaceutical industries.

This work describes research focused on the recovery of ellagic acid (EA) using solid-state fermentation-assisted extraction (SSF) with Aspergillus niger GH1 and Mexican rambutan peel as support. Several culture conditions (temperature, initial moisture, levels of inoculum, and concentration of salts) were evaluated using a Placket–Burman design (PBD) for screening culture factors followed by a central composite design (CCD) for enhancing the EA. Antioxidant activity and polyphenol content were evaluated in SSF. Temperature (28.2 °C), inoculum (2 × 10⁷ spores/g), and NaNO₃ (3.83 g/L) concentration were identified as a significant parameter for EA in SSF. This enhancing procedure resulted in an increase in EA recovery [201.53 ± 0.58–392.23 ± 17.53 mg/g] and, with two steps of purification, [396.9 ± 65.2 mg/g] of EA compound was recovered per gram of recovered powder. Fermentation extracts reflect inhibition of radicals and the presence of polyphenol content. This work proposes to identify the ideal conditions of fermentation in order to obtain a higher yield high-quality compound from agro-industrial wastes through SSF.

Rambutan (Nephelium lappaceum L.) is a tropical fruit that is originally from Southeast Asia and it was introduced to Mexico in the 1960s; the fruit’s peel is known to possess ellagitannins such as ellagic acid which give the peel great biological activity; solid-state fermentation has been used to obtain said compounds and rambutan peel can be used as a fermentation support/substrate; this work aims to obtain, identify and quantify ellagic acid obtained via SSF with a strain of yeast. The water-absorption index and the support’s maximum moisture were determined. To determine the ideal conditions for ellagic acid accumulation, a Box–Behnken 3^k experimental design was applied using variables such as temperature, moisture and inoculum. The maximum accumulation time of ellagic acid via solid-state fermentation was determined to be 48 h with ideal conditions of 30 °C, 60% moisture and 1.5 × 10⁷ cells/g using S. cerevisiae, and high-performance liquid chromatography was used to identify ellagic acid, geraniin and corilagin as the most abundant compounds. The maximum recovery of ellagic acid was 458 ± 44.6 mg/g. HPLC/ESI/MS analysis at 48 h fermentation showed biodegradation of geraniin and corilagin due to ellagic acid. Mexican rambutan peel has been demonstrated to be a suitable substrate for SSF.

Rambutan peel is a great source of bioactive compounds, the same that, over the years, has been extracted using conventional technologies which have been proven to be harmful to the environment and potentially toxic to human beings. This study aimed to extract the same compounds using a hybridization of ultrasound/microwave extraction. The results were promising, as a total of 378.48 ± 9.19 mg/g of polyphenols were recovered from this procedure, and the most important molecules (geraniin, corilagin, and ellagic acid) were identified, giving this much more relevance. Furthermore, treatment with rambutan peel extract recovered with green technologies significantly reduced cell viability in HCV-infected liver cells. Notably, higher concentrations (4000 and 5000 ppm) led to more pronounced cell death in huh7 cells. The treatment also led to a significant reduction in viral protein and RNA expression in HCV-infected cells. These findings suggest that rambutan peel extract obtained from the combination of ultrasound and microwave extraction, particularly the ellagitannins present, have potential antiviral properties. Further research is needed to explore its mechanism of action and its potential as a therapeutic agent for Hepatitis C.

Bioactive compounds are secondary metabolites widely studied for their benefits to human health. They are distributed in various fruit, vegetable, and plant peels. The application of sustainable techniques for the extraction of these compounds is being implemented, assisted extraction by solid-state fermentation is a sustainable and effective alternative for the recovery of bioactive compounds by using agro-industrial waste as a raw material for extraction, this being a green process, easy for implementation, and it has low water and energy consumption. This research presents the biological properties of some of the most used bioactive compounds in the industry, as well as the advantages and factors that influence solid-state fermentation and the different processes for their recovery and/or production. The production of bioactive compounds using both continuous and discontinuous processes come with unique advantages and challenges. The choices between these methods depend on specific production objectives, scalability needs, and the availability of resources. As a result, ongoing advancements are refining these methods, enabling more sustainable and efficient production of bioactive compounds.

Ellagitannins (ETs) derived from rambutan (Nephelium lappaceum L.) peel are polyphenols that have gained prominence in the food and nutraceutical industries due to their high bioactivity. The objective of this study was to evaluate the encapsulation efficiency (EE) of ETs obtained from rambutan peel in sodium alginate beads, as well as their effect on cell viability and antioxidant potential. ETs were extracted and semi-purified using Amberlite XAD-16 resin and identified by HPLC/ESI/MS. To determine the encapsulation efficiency, a 3^k Box–Behnken experimental design was employed, evaluating the influence of ET concentration (1000, 2000, and 3000 ppm), sodium alginate (1, 2, and 3%), and CaCl₂ (5, 10, and 15 mM). Cell viability was assessed in HEK-293 and 3T3 cell lines, and antioxidant potential was determined through ABTS, DPPH, and FRAP assays. The results showed a maximum EE of 55% under conditions of 3000 ppm ETs, 2% sodium alginate, and 5 mM CaCl₂. Cell viability assays confirmed that both the crude extract and the ET-loaded capsules possess excellent biocompatibility, maintaining values above 70%. Furthermore, the capsules demonstrated significant antioxidant potential (ABTS 76%, DPPH 65%, FRAP 1.11 mmol TE/L) compared to the control (sodium alginate). These findings position the ET-loaded rambutan peel capsules as a promising alternative for the development of functional products in the food industry.