Evaluation of Sweet Orange (<i>Citrus sinensis</i>) Waste-Derived Pectin as a Sustained Release Excipient in Matrix Tablets of Nifedipine

Abstract

Pectin is a natural polymer that has a wide range of pharmaceutical applications including in controlled drug delivery. The annual orange  production of Ethiopia is reported to be about 26,000 tons in 2022. From this amount, the peels account for 30 - 40% of the total weight of  the fresh fruit which are damped as a waste material resulting in ecological and economic burden of disposing the accumulated waste  products. This waste material can be converted to 590 - 780 tons of pectin annually, generating a huge sum of money. The objective of  this research work was to isolate and characterize the physicochemical properties of orange peel (Citrus sinensis) waste-derived pectin as  a matrix-forming polymer for sustained release tablet formulations using nifedipine as a model. Pectin was extracted from the dried  orange peel powder by acidified hot water extraction method. The extracted pectin was found to be a non-free-flowing, poorly compressible powder with a degree of methyl esterification of 39% and is classified as low methoxy pectin. The galacturonic acid (GalA)  content of the extracted pectin was found to be 90 ± 2%. Pectin-based matrix tablets of nifedipine were prepared by the non-aqueous wet  granulation method with and without incorporating zinc chloride and calcium chloride and showed successful sustained release  effect. The weight variation, hardness, friability, tensile strength, and disintegration time of the formulations were within acceptable  ranges. The formulated matrix tablets sustained the drug release for more than 12 h. At equal concentrations, zinc pectinate showed a  better sustaining effect than calcium pectinate. The drug release data were fitted into different release kinetics models and the Hixson- Crowell model best fitted the release data. In conclusion, Citrus sinensis peel waste-derived pectin can be employed as a safe natural  excipient in a sustained drug delivery system.