Shahrekord University of Medical Sciences Journal of Herbmed Pharmacology 2345-5004 14 3 2025 07 01 Phytochemical profiling, antioxidant potential, and anti-Acinetobacter baumannii activity of Macadamia integrifolia Maiden & Betche shell extracts 339 347 10.34172/jhp.2025.53018 EN Khemmachat Pansooksan https://orcid.org/0009-0007-7318-7055 Chanakan Chailom https://orcid.org/0009-0001-9666-8624 Naphat Kaewpaeng https://orcid.org/0009-0007-3596-5426 Sirintorn Pisutthanan https://orcid.org/0000-0001-9199-7990 Nantida Rittaisong https://orcid.org/0009-0001-1946-7941 Leefong Yau https://orcid.org/0000-0001-9627-0088 Dumrongsak Pekthong https://orcid.org/0000-0001-8965-3435 Piyarat Srisawang https://orcid.org/0000-0002-0948-8239 Nareeluk Nakaew https://orcid.org/0009-0000-0667-3247 Supawadee Parhira https://orcid.org/0000-0002-2077-5888 Journal Article 10.34172/jhp.2025.53018 2025 03 13 2025 05 27 Introduction: Macadamia integrifolia Maiden & Betche shells, which comprise approximately 80% of the total fruit weight and are often regarded as a by-product of macadamia nut production, contain bioactive compounds with potential health benefits. However, few studies have investigated the bioactive properties of M. integrifolia shells for pharmaceutical, cosmetic, and food applications. Therefore, this study aimed to evaluate the phytochemical contents, antioxidant activity, and inhibitory effects against Acinetobacter baumannii of M. integrifolia shell extracts. Methods: Shell powder of M. integrifolia was extracted using 95% ethanol to yield a crude extract (ME), which was subsequently fractionated into dichloromethane (MD), ethyl acetate (MA), and water (MW) fractions. Total phenolic and flavonoid contents were determined using colorimetric assays. Antioxidant and antimicrobial activities were assessed via the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and disc diffusion method, respectively. Results: The M. integrifolia shell extracts (ME, MD, MA, and MW) contained total phenolic contents ranging from 4.27 to 26.76 mg gallic acid equivalent/g and flavonoid contents from 7.93 to 38.01 mg rutin equivalent/g. The MA fraction demonstrated the most potent antioxidant activity (IC₅₀ = 17.60 µg/mL). All extracts showed inhibitory effects against A. baumannii, with inhibition zones between 7.0 and 12.0 mm; the ME extract exhibited the largest inhibition zone (12.0 mm). Conclusion: This is the first report to demonstrate the antioxidant and antimicrobial activities of M. integrifolia shell extracts against A. baumannii. Their high phenolic and flavonoid contents support potential use as natural bioactive agents. Further studies on biomarkers purification and the mechanism of action are recommended.