The recent millennium has witnessed a notable shift in consumer focus towards natural products for addressing lifestyle-related disorders, driven by their safety and cost-effectiveness. Nutraceuticals and functional foods play an imperative role by meeting nutritional needs and offering medicinal benefits. With increased scientific knowledge and awareness, the significance of a healthy lifestyle, including diet, in reducing disease risk is widely acknowledged, facilitating access to a diverse and safer diet for longevity. Plant-based foods rich in phytochemicals are increasingly popular and effectively utilized in disease management. Agricultural waste from plant-based foods is being recognized as a valuable source of nutraceuticals for dietary interventions. Citrus peels, known for their diverse flavonoids, are emerging as a promising health-promoting ingredient. Globally, citrus production yields approximately 15 million tons of by-products annually, highlighting the substantial potential for utilizing citrus waste in phyto-therapeutic and nutraceutical applications. Citrus peels are a rich source of flavonoids, with concentrations ranging from 2.5 to 5.5 g/100 g dry weight, depending on the citrus variety. The most abundant flavonoids in citrus peel include hesperidin and naringin, as well as essential oils rich in monoterpenes like limonene. The peel extracts exhibit high antioxidant capacity, with DPPH radical scavenging activities ranging from 70 to 90%, comparable to synthetic antioxidants like BHA and BHT. Additionally, the flavonoids present in citrus peel have been found to have antioxidant properties, which can help reduce oxidative stress by 30% and cardiovascular disease by 25%. Potent anti-inflammatory effects have also been demonstrated, reducing inflammatory markers such as IL-6 and TNF-α by up to 40% in cell culture studies. These findings highlight the potential of citrus peel as a valuable source of nutraceuticals in diet-based therapies.

An investigation into the efficient use of water as a solvent and the influence of extraction temperature, extraction time, water to leaf powder ratio, particle size, and extraction cycle on the nutraceutical and antioxidant profile of aqueous mulberry leaf extract were conducted using a single-factor experiment approach. All the assessed extracting parameters showed a significant effect on the nutraceutical compounds and antioxidant properties. The optimum extraction conditions were as follows: extraction temperature of 70°C, extraction time of 40 min, water to leaf powder ratio of 40:1 ml/g, particle size of 25 µm, and two extraction cycles. Based on these optimal conditions, chlorogenic acid (62.10 mg/g), caffeic acid (32.21 mg/g), kaempferol-7-O-glucoside (19.30 mg/g), quercetin-3-rutinose (15.69 mg/g), quercetin-3-O-glucoside (32.38 mg/g), kaempferol-3-(6-rhamnosylglucoside) (42.52 mg/g), quercetin-3-(6-malonylglucoside) (65.19 mg/g), kaempferol-3-glucoside (66.27 mg/g), kaempferol-3-(6-malonylglucoside) (50.18 mg/g), 1-deoxynojirimycin (15.58 mg/g), and gamma-aminobutyric acid (5.05 mg/g) were obtained. The optimal aqueous extract had high antioxidant properties of 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (39.98 mM/g), cupric ion reducing capacity (58.93 mM/g), 1,1-diphenyl-2-picrylhydrazyl (101.33 mM/g), and ferric reducing antioxidant power capacity (233.77 mM/g) of dried mulberry leaf extract.