Capsaicin is an active compound in chili peppers (Capsicum chinense) that has been approved for chronic pain treatment. The topical application of high-strength capsaicin has been proven to reduce pain; however, skin irritation is a major drawback. The aim of this study was to investigate an appropriate and scalable technique for preparing nanostructured lipid carriers (NLCs) containing 0.25% capsaicin from capsicum oleoresin (NLC_C) and to evaluate the irritation of human skin by chili-extract-loaded NLCs incorporated in a gel formulation (Gel NLC_C). High-shear homogenization with high intensity (10,000 rpm) was selected to create uniform nanoparticles with a size range from 106 to 156 nm. Both the NLC_C and Gel NLC_C formulations expressed greater physical and chemical stabilities than the free chili formulation. Release and porcine biopsy studies revealed the sustained drug release and significant permeation of the NLCs through the outer skin layer, distributing in the dermis better than the free compounds. Finally, the alleviation of irritation and the decrease in uncomfortable feelings following the application of the Gel NLC_C formulation were compared to the effects from a chili gel and a commercial product in thirty healthy volunteers. The chili-extract-loaded NLCs were shown to be applicable for the transdermal delivery of capsaicin whilst minimizing skin irritation, the major noncompliance cause of patients.

This study aimed to characterize and investigate the potential of the oils from Gryllus bimaculatus, Teleogryllus mitratus, and Acheta domesticus to be used in nanoemulsions. The oils were extracted by a cold press method and characterized for their fatty acid profiles. Their irritation effects on the chorioallantoic membrane (CAM) were evaluated, along with investigations of solubility and the required hydrophilic–lipophilic balance (RHLB). Various parameters impacting nanoemulsion generation using high-pressure homogenization were investigated. The findings revealed that G. bimaculatus yielded the highest oil content (24.58% w/w), followed by T. mitratus (20.96% w/w) and A. domesticus (15.46% w/w). Their major fatty acids were palmitic, oleic, and linoleic acids. All oils showed no irritation, suggesting safety for topical use. The RHLB values of each oil were around six–seven. However, they could be successfully developed into nanoemulsions using various surfactants. All cricket oils could be used for the nanoemulsion preparation, but T. mitratus yielded the smallest internal droplet size with acceptable PDI and zeta potential. Nanoemulsion was found to significantly enhance the antioxidant and anti-skin wrinkle of the T. mitratus oil. These findings pointed to the possible use of cricket oils in nanoemulsions, which could be used in various applications, including topical and cosmetic formulations.

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.

Background/Objectives: This study aimed to develop a nanostructured lipid carrier (NLC) system incorporating a catechin-rich Vanda coerulea extract for topical cosmetic applications and to evaluate its physicochemical properties, release behavior, and skin retention performance. Methods: Blank NLCs were prepared using hot emulsification followed by sonication, with glyceryl monostearate, caprylic triglyceride, Poloxamer^® 188, and Tween^® 80 as the formulation components. NLCs with varying solid-to-liquid lipid ratios were developed while maintaining a constant total lipid content of 5% w/w. The formulations were characterized based on their particle size, polydispersity index (PDI), zeta potential, and physical stability, including stability after a heating–cooling cycle test. The effect of ultrasonication duration was also evaluated. The optimized NLC was then loaded with a V. coerulea extract and evaluated for in vitro release and skin retention using catechin as a marker. Results: The NLC with a particle size of 235.5 ± 29.8 nm, a narrow PDI range of 0.382 ± 0.090, and a strong zeta potential of −29.8 ± 0.3 mV was selected for the incorporation of the V. coerulea extract. The extract-loaded NLC exhibited a sustained release over 24 h, significantly different from the V. coerulea extract solution (p < 0.05). Skin retention studies revealed that the NLC achieved approximately twice the catechin retention compared to the solution at the 1 h time point (1.30 ± 0.01% vs. 0.68 ± 0.03% w/w). Conclusions: The V. coerulea-extract-loaded NLC demonstrated favorable physicochemical properties, sustained release behavior, and enhanced skin retention. These findings support its potential as a promising topical delivery system for antioxidant-rich botanical extracts in cosmetic applications.