Characterization of Green and Yellow Papaya (<i>Carica papaya</i>) for Anti-Diabetic Activity in Liver and Myoblast Cells and Wound-Healing Activity in Fibroblast Cells

Obesity and diabetes, often characterized as “metabolic syndrome”, have been recognized as two of the most important public health issues worldwide. The objective of the present research was to evaluate green and yellow papaya for anti-oxidation and anti-diabetic properties. Leaves, skin, pulp, and seed samples from papayas were freeze-dried and then extracted in water or 80% methanol. The extracts were used to determine total polyphenolic content and anti-oxidation activities, and to determine biological activities, including glucose uptake, Glut-2 expression, triglyceride reduction, and wound-healing activity. Our data demonstrated that methanol and water extracts of green and yellow papaya have similar concentrations of polyphenols in skin (10–20 mg/g dry powder), leaf (25–30 mg/g dry powder), and pulp (1–3 mg/g dry powder) fractions. However, both methanol and water extracts of seeds from yellow papaya have substantially higher concentrations of polyphenols compared to green papaya. Both water and methanol extracts of yellow papaya exhibited higher anti-oxidation activity compared to green papaya in skin (50–60%), pulp (200–300%), and seeds (10–800%). Old leaves also showed greater anti-oxidation activity (30–40%) compared to new leaves. Pulp extracts from both yellow and green papaya stimulated greater glucose uptake, but only pulp from green papaya stimulated glucose uptake in muscle cells. Similarly, pulp extract stimulated glucose transporter Glut-2 expression in liver cells. The skin, pulp, and seeds of green or yellow papaya showed triglyceride-lowering activity in liver cells by 60–80%, but samples taken from yellow papaya had a more potent effect. Seeds from both green and yellow papaya significantly stimulated the migration of fibroblasts in the wounded area by 2–2.5-fold compared to the untreated control. Consistent with these data, seeds from both green and yellow papaya also significantly stimulated collagen synthesis in fibroblast cells by almost 3-fold. In conclusion, our data indicate that different parts of papaya produce stimulatory effects on glucose uptake, Glut-2 expression, TG reduction, and wound-healing activities. This study concludes that different parts of the papaya can be beneficial for preventing diabetes and diabetes-related wound healing

Functional foods as source of bioactive principles. Some marked examples

Functional foods are those that have a beneficial effect on health beyond the basic function of nutrition, helping to promote better health conditions and to reduce the risk of various diseases. This concept was created in Japan in the 1980s and is widely used around the world. The regulation of these products is made by different authorities and has not been defined yet in many countries. The field of food production has increased and changed considerably in the last decades, since the consumers believe that foods, besides satisfy hunger and to provide necessary nutrients for humans, also contribute directly to improve their health conditions. The present chapter will focus with marked examples the main categories of functional foods and respective therapeutic potential (cardioprotective, hepatoprotective, hypolipidemic, antioxidant, anticancer, anti-inflammatory properties, etc.) as well as the active principles responsible for the medicinal properties (flavonoids, alkaloids, terpenes, etc.), including curcuma, garlic, olive oil, grape, broccoli, and probiotic, among others