Phytochemical analysis of green-branch bark extract and the brown gum exudates “kinos” from Eucalyptus camaldulensis by HPLC and GC–MS with their antifungal activity

Abstract

Eucalyptus has been utilized in traditional Australian medicines for the treatment of various ailments and is also used in pharmaceutical and cosmetic products. Eucalyptus contains an important source of key bioactive volatile and nonvolatile compounds. With the increasing research interest in Eucalyptus extracts and their health properties as an eco-friendly treatment, the green-branch bark extract (GBE) and the brown gum exudates, known as "kinos," from Eucalyptus camaldulensis Dehnh. grown in Egypt, were used as biofungicide agents applied to Pinus halepensis Mill. wood samples. The phytochemicals were analyzed using the chromatographic tools, HPLC and GC-MS. These extracts at concentrations of 125, 250, 500, and 1000 µg/mL were further tested for their antifungal activity against Fusarium circinatum and Pythium tardicrescens, which were isolated from the diseased roots of Pinus halepensis. HPLC analysis of GBE revealed that kaempferol (14043.15 µg/g extract), gallic acid (7021.37 µg/g extract), and ellagic acid (4983.92 µg/g extract) were the major compounds. In the kinos, the main compounds were chlorogenic acid (12511.35 µg/g extract), gallic acid (12443.92 µg/g extract), ellagic acid (8147.54 µg/g extract), and rutin (2025.87 µg/g extract). By the GC-MS, p-cymene (31.91%), spathulenol (26.56%), and crypton (11.60%) were detected as primary compounds in the GBE. In the kinos, the abundant identified compounds by GC-MS were spathulenol (19.61%), isoaromadendrene epoxide (9.13%), α-acorenol (4.71%), and patchoulane (4.68%). Both GBE and kinos showed potential antifungal activity at 1000 µg/mL, inhibiting F. circinatum growth with fungal inhibition percentage (FIP) values of 71.85% and 71.11%, respectively. The GBE at 1000 and 500 µg/mL exhibited the highest antifungal effects against P. tardicrescens, with FIP values of 39.62% and 35.55%, respectively. The primary uniqueness of research into green-branch bark extracts and kinos from Eucalyptus camaldulensis comes from the growing global problem of antifungal resistance and the pressing need to identify specific bioactive chemicals for innovative development and investigate their application in environmentally friendly wood-biofungicide applications.