Mitragyna speciosa (kratom) is a traditional medicinal plant rich in bioactive alkaloids and phenolics, known for their antioxidant and anti-aging properties. This study aimed to develop nanoparticle-based topical gels from ethanolic extracts of four kratom varieties, including Kan Daeng (KD), Hang Kang (HK), Tai Bai-yao (KY), and Kan Keaw (KG). Kratom NPs were prepared using a solvent displacement method. The resulting nanoparticles (NPs) exhibited sizes of 201.9–256.2 nm, polydispersity indices (PDI) below 0.3, and a zeta potential between −22.6 and −29.6 mV. The phytochemical analysis revealed that KG and KY extracts contained the highest total phenolic content (TPC) and total flavonoid content (TFC), which were mostly retained after NP formulation. The HPLC analysis confirmed HK as the richest source of mitragynine (9.97 ± 0.10% w/w), while NP formulations displayed slightly reduced levels. Antioxidant activities assessed by DPPH, ABTS, and FRAP assays revealed enhanced radical scavenging in nanoparticle formulations, with IC₅₀ values ranging from 151.23 to 199.87 µg/mL (DPPH) and 207.37 to 272.83 µg/mL (ABTS). All formulations exhibited a significant inhibition of collagenase (80.56 ± 1.60 to 97.23 ± 0.29%), elastase (45.46 ± 6.53 to 52.19 ± 1.20%), and hyaluronidase (83.23 ± 2.34 to 91.67 ± 3.56%), with nanoparticle forms showing superior enzyme inhibition. Notably, nanoparticle formulations exhibited superior inhibitory effects compared to crude extracts. HaCaT cytotoxicity tests confirmed high biocompatibility (IC₅₀ > 700 µg/mL), especially for KD and KG NPs. The NP-loaded gels demonstrated acceptable physicochemical stability after heating/cooling cycle testing, with pH (7.27 to 7.88), viscosity (10.719 to 12.602 Pa·s), and favorable visual and textural properties. In summary, KG and KY cultivars emerged as the most promising cosmeceutical candidates due to their superior phytochemical content, antioxidant capacity, enzyme-inhibitory activities, and formulation performance. These findings support the potential use of KG NP and KY NP-loaded gels as multifunctional cosmeceutical agents for antioxidant protection, anti-aging, and skin rejuvenation.

Kratom (Mitragyna speciosa Korth.) has gained increasing global attention due to its traditional use, psychoactive properties, and emerging therapeutic potential; however, concerns regarding adulteration, substitution, and inconsistent quality of commercial products necessitate robust authentication strategies. This study aimed to integrate DNA barcoding and comprehensive chemical profiling to authenticate kratom variants and discriminate them from closely allied Mitragyna species for quality control and forensic applications. Nine DNA barcoding regions were analyzed, alongside chemical characterization using UHPLC, GC–MS, and LC–MS/QTOF. Among the tested loci, the internal transcribed spacer (ITS) and ITS2 regions exhibited the highest interspecific variation and effectively distinguished kratom from allied species. UHPLC and GC–MS analyses confirmed that mitragynine was exclusively detected in kratom variants, with Kan Khiao exhibiting the highest content (94.33 ± 0.14 mg/g) when quantified against the mitragynine standard using UHPLC analysis. LC–MS/QTOF profiling revealed an alkaloid-rich chemotype in kratom dominated by mitragynine and 7-hydroxymitragynine, whereas M. diversifolia, M. hirsuta, and M. rotundifolia showed distinct profiles enriched in phenolic acids and flavonoid glycosides. Multivariate analyses further identified procyanidin B1, datiscetin-3-O-rutinoside, mitragynine, and 7-hydroxymitragynine as key discriminatory markers. Overall, the combined molecular and chemical workflow provides a robust framework for kratom authentication, supporting regulatory monitoring, quality assurance, and forensic identification of kratom materials.