Extraction of active compounds from traditional herbal compress ingredients for hydrogel pain relief patch development

Abstract

Importance of the work: The modification of traditional herbal compresses into easy-touse patches provides a more convenient alternative while delivering equivalent benefits to other commercial products. Objectives: To extract active compounds for herbal compresses for the development of pain relief patches. Materials and Methods: Samples of the Thai herb ‘plai’ (Zingiber cassumunar Roxb.), turmeric (Curcuma longa L.) and Centella asiatica (L.) Urb., were extracted using steam distillation, water extraction or frying with coconut oil. Then, the active compounds were analyzed using gas chromatography-mass spectrometry (GC-MS) and Fourier-transform infrared spectroscopy (FTIR) to identify their components. Subsequently, these extracts were incorporated into pain relief patches formulated with a pectin and sodium alginate base. Results: The extracts from the three plants were analyzed using GC-MS, identifying γ- terpinene at 11 min, (E)-1-(3,4-dimethoxyphenl) butadiene at 29 min and levomenthol at 18 min as pain-relieving compounds. The FTIR analysis of the extracts and pain relief patches detected functional groups, consisting of C=C bending, C-O stretching, N-O stretching, C=O stretching, C-H stretching and O-H stretching. An irritation test using the 4 hr closed patch method at 0 hr, 4 hr, 24 hr, 48 hr and 72 hr resulted in no significant (p < 0.05) skin irritation. Main finding: The extracts were incorporated effectively into a pectin-sodium, alginate, hydrogel matrix, forming structurally stable patches, as confirmed by scanning electron microscopy-energy-dispersive X-ray spectroscopy and FTIR analyses. Skin irritation testing demonstrated excellent biocompatibility, while volunteer-based evaluation showed significant pain reduction after application. Based on these results, the developed hydrogel patch represented a practical and user-friendly alternative to conventional herbal compresses, bridging traditional medicine with modern transdermal delivery systems.