Quantification of phytochemicals of different parts of Oroxylum indicum (L.) Kurz for the evidence-based substitution of the official part (root) with aerial part

Oroxylum indicum (L.) Kurz (OI) or Shyonaka or Sona Patha is an endangered medicinal plant used in various traditional medicines. The roots of OI are the most commonly used part in preparing numerous traditional medicines worldwide. To conserve the environment, it is necessary to check the substitution of official parts with aerial parts like leaf and stem bark using sophisticated techniques. The present study developed HPLC and ICP-OES methods to quantify OI's main phytoconstituents and metal ions in four parts (root, root bark, stem bark, and leaf). The phytochemicals viz. vanillic acid, trans-ferulic acid, baicalein, and chrysin were quantified by HPLC study, where the significantly better amounts of baicalein and chrysin (baicalein > chrysin) were quantified in aerial parts (leaf and stem bark) as compared to root and root bark. ICP-OES elemental analysis has revealed that all parts of OI are good sources of Ca, K, Na, Mg, Mn, Fe, and Zn. GC–MS study was performed to identify the volatile compounds of all parts of OI. In antioxidant studies (TPC, TFC, and DPPH assays), the leaf showed a better IC₅₀ value, followed by stem bark, root bark, and root. In the antacid study, the leaf has shown better activity, followed by root bark, stem bark, and root. In the anti-bacterial assay, all parts of OI significantly inhibited Staphylococcus aureus and Salmonella typhi strains, where root bark and leaf demonstrated improved activities. In computational studies, the invitro antacid, antioxidant, and anti-bacterial activities were confirmed, where most of the phytochemicals demonstrated binding energies over standard drugs. Overall, the study revealed that all parts of OI, including roots and aerial parts, might be medicinally useful, and leaves may be used as a nutritional food. Moreover, the official part, i.e., root or root bark used in traditional medicines, may be replaced with aerial parts (leaf or stem bark) to conserve the environment. After the in-depth pharmacological and toxicological studies, all parts of OI Oroxylum indicum might be incorporated into pharmaceutics.