Leaves of Moringa oleifera Are Potential Source of Bioactive Compound β-Carotene: Evidence from In Silico and Quantitative Gene Expression Analysis

Moringa oleifera is rich in bioactive compounds such as beta-carotene, which have high nutritional values and antimicrobial applications. Several studies have confirmed that bioactive-compound-based herbal medicines extracted from the leaves, seeds, fruits and shoots of M. oleifera are vital to cure many diseases and infections, and for the healing of wounds. The β-carotene is a naturally occurring bioactive compound encoded by zeta-carotene desaturase (ZDS) and phytoene synthase (PSY) genes. In the current study, computational analyses were performed to identify and characterize ZDS and PSY genes retrieved from Arabidopsis thaliana (as reference) and these were compared with the corresponding genes in M. oleifera, Brassica napus, Brassica rapa, Brassica oleracea and Bixa orellana. The BLAST results revealed that all the plant species considered in this study encode β-carotene genes with 80–100% similarity. The Pfam analysis on β-carotene genes of all the investigated plants confirmed that they belong to the same protein family and domain. Similarly, phylogenetic analysis revealed that β-carotene genes of M. oleifera belong to the same ancestral class. Using the ZDS and PSY genes of Arabidopsis thaliana as a reference, we conducted qRT-PCR analysis on RNA extracted from the leaves of M. oleifera, Brassica napus, Brassica rapa and Bixa orellana. It was noted that the most significant gene expression occurred in the leaves of the studied medicinal plants. We concluded that not only are the leaves of M. oleifera an effective source of bioactive compounds including beta carotene, but also the leaves of Brassica napus, Brassica rapa and Bixa orellana can be employed as antibiotics and antioxidants against bacterial or microbial infections.