Khemmachat Pansooksan
1,2 
, Chanakan Chailom
1,2 , Naphat Kaewpaeng
1,2 , Sirintorn Pisutthanan
1 , Nantida Rittaisong
3 , Leefong Yau
4 , Dumrongsak Pekthong
2,5,6 , Piyarat Srisawang
2,7,8 , Nareeluk Nakaew
9,10* , Supawadee Parhira
2,6,11* 1 Department of Pharmaceutical Chemistry and Pharmacognosy, Faculty of Pharmaceutical Sciences, Naresuan University, Phitsanulok, 65000, Thailand
2 Center of Excellence for Innovation in Chemistry, Naresuan University, Phitsanulok, 65000, Thailand
3 Division of Applied Thai Traditional Medicine, Faculty of Public Health, Naresuan University, Phitsanulok, 65000, Thailand
4 State Key Laboratory of Quality Research in Chinese Medicine, Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Taipa, 999078, Macao, China
5 Department of Pharmacy Practice, Faculty of Pharmaceutical Sciences, Naresuan University, Phitsanulok, 65000, Thailand
6 Center of Excellence for Environmental Health and Toxicology, Faculty of Pharmaceutical Sciences, Naresuan University, Phitsanulok, 65000, Thailand
7 Department of Physiology, Faculty of Medical Science, Naresuan University, Phitsanulok, 65000, Thailand
8 Center of Excellence in Medical Biotechnology, Faculty of Medical Science, Naresuan University, Phitsanulok, 65000, Thailand
9 Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Phitsanulok, 65000, Thailand
10 Center of Excellence in Fungal Research, Faculty of Medical Science, Naresuan University, Phitsanulok, 65000, Thailand
11 Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Naresuan University, Phitsanulok, 65000, Thailand
Abstract
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.
Implication for health policy/practice/research/medical education:
Macadamia integrifolia shell extracts exhibit antioxidant potential and antimicrobial activity against Acinetobacter baumannii. These findings highlight their pharmaceutical, cosmetic, and food application research promise. Further studies on biomarkers purification and the mechanism of action are recommended.
Please cite this paper as: Pansooksan K, Chailom C, Kaewpaeng N, Pisutthanan S, Rittaisong N, Yau L, et al. Phytochemical profiling, antioxidant potential, and anti-Acinetobacter baumannii activity of Macadamia integrifolia Maiden & Betche shell extracts. J Herbmed Pharmacol. 2025;14(3):339-347. doi: 10.34172/jhp.2025.53018.