Authenticating Basil (Ocimum spp.): An Integrated Quality Control Strategy

Standardisation is essential to ensure the quality, efficacy, and safety of basil oil products. Although Ocimum basilicum L. is the most widely traded species, other Ocimum species are often sold under the same name, increasing the risk of misidentification and adulteration. Intraspecific variation in morphology and chemical composition further complicates standardisation, highlighting the need for a comprehensive authentication strategy. This study evaluates genetic, chemical, and morphological methods for the authentication of commercial basil accessions to support accurate species identification and product standardisation. Samples were analysed using DNA barcoding (matK, trnH-psbA, rbcL, rpl16), GC-MS-based chemical profiling, and trichome characterisation via scanning electron microscopy. Phylogenetic analysis placed all commercial samples within a broad clade encompassing O. basilicum, its hybrids, and related species. Species-specific single nucleotide variations in matK and trnH-psbA supported the identification of distinct accessions. Notably, liquorice basil showed genetic similarities to non-basilicum species, suggesting the need to revisit its classification. Chemical profiling revealed substantial variation in essential oil composition, with some samples dominated by linalool and eugenol, and others by methyl chavicol, raising potential safety concerns. Morphological analysis further highlighted differences in trichome density, particularly in the blue spice variety. The findings underscore the limitations of using a single method for basil authentication and advocate for an integrated approach. DNA barcoding supports species identification, while chemical profiling is essential for chemotype differentiation. Developing reliable DNA markers and incorporating combined analyses into routine quality control can strengthen industry standards for natural product authentication.