Phytochemical analysis and preliminary pharmacological evaluation of horse apple as a sustainable source for bioactive isoflavones

Abstract

T fruit of Maclura pomifera tree (Raf.) Schneid. (family Moraceae), commonly known as horse apple, has traditionally been used as an insect repellant and its extract is a strong antioxidant. The major constituents of horse apple are the prenylated isoflavones pomiferin and osajin which are responsible for its antioxidant activity as well as other activities, such as cardioprotective and antitumor effects. The tree grows in Southern United States and the Midwest and produces its fruits in abundance during late summer and fall making it a rich and sustainable source for medicinally useful natural products. The first goal of this project was to identify horse apple sources and the best sample preparation procedures leading to extracts with high isoflavone content. The second goal was to investigate the activity of horse apple in new targets for certain disease conditions. To achieve the first goal, a reversed-phase HPLC method was developed, validated and applied to determine the effect of geographical location, degree of development and sample preparation on the levels of pomiferin and osajin in horse apple. For the second goal, the total methanolic extract was evaluated in two panels of in vitro assays for anti-inflammatory activity (inhibition of iNOS and NF-kB/induction of NAG), and inhibition of tau protein fibrillation. Phytochemical analysis indicated that the isoflavone content in horse apple may exceed 5% of dry weight and that the degree of maturity of the fruit hasa significant effect on its isoflavone content. Some promising results were also obtained from the preliminary in vitro evaluation of the total extract.