Formulation of roselle extract water-in-oil nanoemulsion for controlled pulmonary delivery

Abstract

The anthocyanin (ACN)-rich roselle extract has the potential to inhibit lung cancer. However, the compounds demonstrate low bioavailability and stability in biological applications. The present study proposed a stable formulation of a water-in-oil (w/o) roselle extract nanoemulsion by combining low (hot temperature inversion) and high-energy approaches (ultrasonication and ultra-homogenization) for pulmonary delivery. The stable w/o formulation comprised of roselle extract (0.04 w/w%), sodium chloride solution (3.0 w/w%), medium-chain triglyceride (81.9 w/w%), surfactant (Tween 80 and Span 80) (15.0 w/w%), hydrophilic-lipophilic balance (HLB) of 6.7 [Tween 80/Span 80 (22.5:77.5)] to yield the stable nanoemulsion.The best nanoemulsion showed an average 298 nm particle size, polydispersity index of 0.6, and zeta potential of −49.0 mV. The emulsions were stable in the centrifuge- and freeze-thaw cycle tests,-alongside the 60-days storage tests at 4 °C, 25 °C, and 35 °C. The in-vitro release of the roselle extract at pH 6.5 buffer was 44.7% and 40.7% at pH 7.4 (p > 0.05), with the release patterns following the non-Fickian diffusion. Hence, the present study successfully developed a stable w/o roselle extract nanoemulsion with a relatively moderate release rate of the ACNs, supporting its suitability as a nanocarrier for pulmonary delivery.

GRAPHICAL ABSTRACT

Keywords:

• Roselle extract
• water-in-oil nanoemulsion
• lung cancer
• physicochemical properties
• in-vitro release

Conflict of interest

The authors declare no conflict of interest.

Additional information

Funding

This research was supported by the Ministry of Education (MOE) through the Fundamental Research Grant Scheme (FRGS/1/2020/ST G01/UTM/02/8).