From botanical waste to a biocatalyst: Kigelia pinnata flower-derived CQDs for triazolidine-3-thione synthesis and their in silico evaluation.

Biowaste-derived carbon quantum dots (CQDs) have emerged as sustainable, low-cost nanomaterials that align with the principles of green chemistry and promote waste-to-wealth conversion. In this work, CQDs were synthesized using drop-down flowers of Kigelia pinnata as a novel biowaste carbon source via a green hydrothermal method. The resulting CQDs were comprehensively characterized by HRTEM, FT-IR, UV-visible, fluorescence spectroscopy, EDS, and XRD, revealing well-dispersed spherical particles with an average diameter of 3.78 nm. They showed excellent catalytic activity as an efficient nanocatalyst for the green synthesis of 1,2,4-triazolidine-3-thione derivatives using ethanol : water (1 : 4) mixture at RT, affording excellent yields (82-97%) in short reaction times (5-20 min). Three of the nine synthesized compounds are new, and the catalyst was reusable for up to six runs without significant loss of activity. The protocol offers key advantages, viz., broad substrate scope, mild conditions, gram-scale feasibility, and favorable green chemistry metrics. Furthermore, all the synthesized compounds were screened for biological activity using PASS prediction, followed by molecular docking with 17β-dehydrogenase (4DBW) and pterin deaminase (3H23). The docking studies showed stable interactions and favorable binding energies, suggesting good affinity for both enzymes. The compounds also exhibited promising drug-like behavior based on ADMET analysis.