Integrative Taxonomic and Chemotaxonomic Authentication of Ageratum conyzoides and Conoclinium coelestinum (Asteraceae): The Pharmacological Annotation Diagnostic Key (PADK), a Reproducible Chemotaxonomic Framework

Ageratum conyzoides L. and Conoclinium coelestinum (L.) DC. are morphologically convergent Asteraceae with overlapping folk-medicinal use across West Africa, and their close resemblance in leaf, root, and inflorescence architecture makes species-level authentication of the medicinal claims attached to each a persistent taxonomic problem. This paper asks whether multiple independent evidence classes can be integrated into a reproducible framework for authenticating such closely related medicinal species, and answers it by constructing the Pharmacological Annotation Diagnostic Key (PADK), an integrative chemotaxonomic authentication framework with pharmacological annotation. Voucher specimens (DELSUH-309, DELSUH-269) from five Delta State localities were authenticated first by gross morphology and developmental anatomy, independently of chemical evidence; volatile chemistry was then profiled by GC-MS (9 compounds in A. conyzoides , 22 in C. coelestinum ) and classified by abundance and distribution; the pharmacological literature for diagnostic markers was then mined under explicit criteria and scored using a mathematically defined Confidence Score and Therapeutic Signature Index. Species identity separated consistently across evidence classes: distinct stem pigmentation and nodal cortex anatomy distinguished the taxa morphologically, while A. conyzoides was chemically dominated by α-phellandrene (34.40%) and C. coelestinum by fatty-acid methyl esters and phytol. Four independently generated evidence classes — morphology, anatomy, chemotaxonomy, and quantitative phytochemistry — converged on the same species separation; on the independent phytochemical dataset, this separation was further confirmed by leave-one-locality-out cross-validation, which correctly classified all ten held-out samples. Annotated pharmacological profiles — led by anti-inflammatory and antinociceptive activity in A. conyzoides and antimicrobial and anti-inflammatory activity in C. coelestinum — were concordant with recorded ethnobotanical use and are reported as literature-derived annotations rather than demonstrated properties. PADK demonstrates feasibility on this species pair and is offered as a transferable template for integrative taxonomic authentication of medicinally important, morphologically difficult plant groups, whose broader applicability remains to be tested.