Preparation of Novel Bio-Sunscreen Using Nanocapsules Encapsulating Pitaya Peel Flavonoids

The peel of the pitaya was the non-edible part of the fruit. It was rich in flavonoids and other bioactive substances. Flavonoids had a variety of beneficial biological properties, including antioxidant, anti-inflammatory, antiviral, anti-tumour and anti-UV properties. However, flavonoids were susceptible to environmental factors such as light, oxygen, pH and temperature, which limited their application. In this study, nanocapsules (HPPF-NC) encapsulating Hylocereus polyrhizus peel flavonoids (HPPF) were prepared. A novel bio-sunscreen (HPPF-NC-SC) containing HPPF-NC was developed. The results showed that HPPF content was 23.81 mg/100 g. HPPF was encapsulated in the nanocapsule structure by hydrophobic interaction. The encapsulation efficiency of HPPF-NC was 67%. HPPF-NC was dissolved in water as smooth spherical particles of various sizes, with an average particle size of 570.58 nm. HPPF-NC showed strong UVA absorption properties and good thermogravimetric stability. HPPF-NC-SC was yellowish in color. HPPF-NC-SC showed the highest sun protection factor (SPF = 47.3) and the best storage stability compared to the extract-free nanocapsulated sunscreen (NC-SC), the sunscreen with free HPPF (HPPF-SC) and the sunscreen without additives (SC). The results of this research improved the stability of flavonoids and expand their new applications in the cosmetics. In addition, it could reduce the waste of natural bio-resources in pitaya peel and realize the high-value utilization of pitaya.