This review provides an overview of recent developments in Citrus aurantium L. (sour or bitter orange), focusing on its bioactive compounds, innovative extraction techniques, and technological applications. C. aurantium is rich in bioactive compounds such as flavonoids (naringin, hesperidin, kaempferol, quercetin), essential oils (β-pinene, limonene), and vitamin C, which represents significant biological activities including antioxidant, antimicrobial, anti-inflammatory, and anticancer effects. The review discusses traditional extraction methods, such as solvent extraction and hydrodistillation, alongside newer, eco-friendly approaches like ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, and natural deep eutectic solvents. It also highlights cutting-edge techniques, including molecular imprinting polymer-based extraction, which enable the more efficient enrichment and purification of specific compounds like synephrine. Finally, the review examines the diverse industrial applications of these bioactive compounds in sectors such as foods, pharmaceuticals, and cosmetics, while emphasizing the growing need for sustainable and efficient extraction technologies.

The aim of this work was to investigate the changes of the content of polyphenols in fruits of Capsicum chinense Jacq. at different harvest times and their correlation with the antioxidant activity. Habanero pepper plants grown in black soil (Mayan name: Box lu’um) and harvested at 160, 209, 223, 237 and 252 post-transplant days (PTD) were analyzed. The results indicated that subsequent harvesting cycles decreased the content of total polyphenols, catechin, chlorogenic acid and ellagic acid, while the content of gallic and protocatechuic acid increased. The antioxidant activity determined by DPPH (2,2-Diphenyl-1-picrylhydrazyl) radical scavenging and ABTS (2,2′-azino-di-3-ethylbenzthiazoline sulfonic acid) assay decreased through the harvest days. Linear correlation analysis between total polyphenol content and antioxidant activity in peppers resulted in a correlation of r²_DPPH = 0.8999 and r²_ABTS = 0.8922. Additionally, a good correlation of the antioxidant activity was found with catechin (r²_DPPH = 0.8661 and r²_ABTS = 0.8989), chlorogenic acid (r²_DPPH = 0.8794 and r²_ABTS = 0.8934) and ellagic acid (r²_DPPH = 0.8979 and r²_ABTS = 0.9474), indicating that these polyphenols highly contributed to the antioxidant activity in Habanero peppers. This work contributes to understanding the changes that take place during the development of Capsicum chinense, indicating that fruit harvested at earlier PTD showed the highest concentrations of total polyphenols and antioxidant activity, obtaining the best results at 160 PTD.

Citrus fruits are widely consumed worldwide; however, one of their primary uses is juice production, resulting in over 40 million tons of agro-industrial waste. Citrus peel is the main agro-industrial by-product in citrus production. In recent years, secondary metabolites of interest, mainly polyphenols such as hesperidin, have been identified in citrus peels. Currently, green alternatives like natural deep eutectic solvents (NADES) based on choline chloride and glucose (Glu), combined with ultrasound-assisted extraction, are studied to obtain polyphenol-rich extracts with potential health applications. This study aims to evaluate the effect of: (1) molar ratios (MR) of 1:0.5, 1:1 or 1:2 mol/mol of choline chloride (ChCl):glucose (Glu); (2) the percentage of added water (WA: 50, 60 or 70%) to NADES; and (3) different citrus peels of Citrus aurantium (bitter orange), Citrus sinensis (sweet orange), and Citrus limon (lemon) used for extraction, on polyphenol profiles, total polyphenol content (TPC), and antioxidant capacity (Ax) of the extracts. The extracts were analyzed using ultra-performance liquid chromatography (UPLC) and evaluated using the Folin–Ciocalteu method for TPC and DPPH assay for quantifying AC. A factorial experimental design 3³ was implemented. The extract obtained with an MR of 1:1 (ChCl:Glu) from Citrus aurantium peel exhibited the highest concentration of hesperidin (2003.37 ± 10.91 mg/100 g dry mass), whereas an MR of 1:2 (ChCl:Glu) exhibited the highest concentration of neohesperidin (1045.94 ± 1.27 mg/100 g dry mass), both using 60% WA. This extract also showed the highest antioxidant capacity, achieving 100% inhibition. On the other hand, the highest concentration of total phenolic content (TPC) (96.23 ± 0.83 mg GAE/100 g dry mass) was obtained using C. aurantium peel with an MR of 1:0.5 (ChCl:Glu) and 60% WA. The extracts also presented high concentrations of rutin and catechin. These findings highlight the potential of revalorizing citrus peels, particularly Citrus aurantium, and their extracts obtained with NADES for possible health applications.

Habanero pepper leaves and stems (by-products) have been traditionally considered waste; however, bioactive compounds such as polyphenols, vitamin C and carotenoids have been identified that can be used for formulation of nutraceuticals or functional foods. Furthermore, the extraction of these bioactive compounds by using environmentally friendly methods and solvents is desirable. Thus, the aim of this study was to assess the antioxidant capacity, total polyphenol content (TPC), the phenolic profile and vitamin C content in extracts obtained from by-products (stems and leaves) of two varieties (Mayapan and Jaguar) of habanero pepper by ultrasound-assisted extraction (UAE) using natural deep eutectic solvents (NADES). The results showed that NADES leads to extracts with significantly higher TPC, higher concentrations of individual polyphenols (gallic acid, protocatechuic acid, chlorogenic acid, cinnamic acid, coumaric acid), vitamin C and, finally, higher antioxidant capacity (9.55 ± 0.02 eq mg Trolox/g DM) than UAE extraction performed with methanol as the solvent. The association of individual polyphenols with NADES was confirmed by principal component analysis (PCA). Overall, NADES is an innovative and promising “green” extraction technique that can be applied successfully for the extraction of phenolic compounds from habanero pepper by-products.

Capsicum chinense Jacq., from the Yucatan peninsula, is recognized worldwide for its pungency, flavor, and secondary metabolites content. This has resulted in an increase in its production, which has led to an increase in the number of byproducts considered waste, mainly its leaves. Capsicum chinense leaves have been demonstrated to contain polyphenols with bioactive properties (antioxidant, anti-inflammatory, antiobesogenic capacity, etc.); hence, the extraction of polyphenols through the use of natural deep eutectic solvents (NADES) with a green technology, such as an ultrasonic probe, could help to revalue these leaves by maximizing the extraction efficiency and preserving their bioactive properties. The objective of this study was to optimize the composition of a eutectic solvent for obtaining an extract rich in polyphenols from the Capsicum chinense leaf using a sonic probe. The optimum conditions of the composition of NADES for obtaining the highest Antioxidant capacity (Ax, 79.71% inhibition) were a 0.8 mol glucose to 1 mol of choline chloride ratio, and 12% water. In addition, with this composition, the Total Polyphenol Content (TPC) obtained was 165.39 mg GAE/100 g dry leaf, and the individual polyphenols, such as vanillin (19.15 mg/100 g dry leaf) and ferulic acid (1.35 mg/100 g dry leaf), were optimized. The habanero pepper leaf extract obtained using a eutectic solvent and a sonic probe demonstrated a high potential for use as an ingredient in the development of nutraceuticals (i.e., functional foods).

Capsicum chinense, commonly known as the habanero pepper, is renowned for its culinary and medicinal value due to a great abundance of polyphenolic compounds. The pursuit of eco-friendly methods for extracting these metabolites, which produce high-purity extracts applicable to the food and pharmaceutical sectors, has led to the adoption of green technologies such as supercritical fluid extraction (SFE). In this methodology, by manipulating factors like temperature, pressure, and extraction time, the goal of producing extracts with elevated phenolic content from plant materials can be achieved. In this study, a central compound design (CCD) was conducted with the response surface methodology (RSM) to optimize the extraction of polyphenols from Capsicum chinense using supercritical fluids. The optimal conditions for total polyphenol extraction were determined as 63.1 °C, 1161.82 psi, and an extraction time of 132 min, with a total polyphenol content (TPC) of 1870 mg of gallic acid equivalent (GAE)/100 g extract. Additionally, concentration of several individual polyphenols were optimized, including catechin (236.27 mg/100 g extract, 62.8 °C, 1150 psi, and 132 min), chlorogenic acid (447.08 mg/100 g extract, 63.1 °C, 1150 psi, and 131.9 min), vanillic acid (136.38 mg/100 g extract, 41.9 °C, 1150 psi, and 132 min), diosmin + hesperidin (92.80 mg/100 g extract, 63 °C, 3200 psi, and 132 min), rutin (40 mg/100 g extract, 63.03 °C, 3200 psi, and 132 min), among others. These findings highlight the potential of supercritical fluid extraction for obtaining high yields of polyphenols from Capsicum chinese. The use of SFE-RSM also may optimize the extraction of specific phenolic compounds, and at the same time, it provides valuable insights for the development of extracts with enhanced bioactive properties for various applications in the food and pharmaceutical industries.