Chemical and biological characterization of Melaleuca subulata (Cheel) Craven leaves' volatile constituents supported by chemometric analysis and molecular docking

Abstract

Background: The genus Melaleuca (Myrtaceae) comprises dozens of essential oil (EO)-rich species that are appreciated worldwide for their various medicinal values. Additionally, they are renowned in traditional medicine for their antimicrobial, antifungal, and other skin-related activities. The current study investigated the chemical profile and skin-related activities of volatile constituents derived from M. subulata (Cheel) Craven (Synonym Callistemon subulatus) leaves cultivated in Egypt for the first time.

Methods: The volatile components were extracted using hydrodistillation (HD), headspace (HS), and supercritical fluid (SF). GC/MS and Kovat's retention indices were implemented to identify the volatile compounds, while the variations among the components were assessed using Principal Component Analysis and Hierarchical Cluster Analysis. The radical scavenging activity was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC) and β-carotene assays. Moreover, the anti-aging effect was evaluated using anti-elastase, and anti-collagenase, while the antimicrobial potential was deduced from the agar diffusion and broth microdilution assays. Lastly, the molecular docking study was executed using C-docker protocol in Discovery Studio 4.5 to rationalize the binding affinity with targeted enzymes.

Results: The SF extraction approach offered the highest EO yield, being 0.75%. According to the GC/MS analysis, monoterpene hydrocarbons were the most abundant volatile class in the HD oil sample (54.95%), with α-pinene being the most copious component (35.17%). On the contrary, the HS and SF volatile constituents were pioneered with oxygenated monoterpenes (72.01 and 36.41%) with eucalyptol and isopulegone being the most recognized components, representing 67.75 and 23.46%, respectively. The chemometric analysis showed segregate clustering of the three extraction methods with α-pinene, eucalyptol, and isopulegone serving as the main discriminating phytomarkers. Concerning the bioactivity context, both SF and HD-EOs exhibited antioxidant effects in terms of ORAC and β-carotene bleaching. The HD-EO displayed potent anti-tyrosinase activity, whereas the SF-EO exhibited significant anti-elastase properties. Moreover, SF-EO shows selective activity against gram-positive skin pathogens, especially S. aureus. Ultimately, molecular docking revealed binding scores for the volatile constituents; analogous to those of the docked reference drugs.

Conclusions: M. subulata leaves constitute bioactive volatile components that may be indorsed as bioactive hits for managing skin aging and infection, though further in vivo studies are recommended.

Keywords: Antibacterial; Antioxidant; Chemometrics; Essential oil; Melaleuca sabulata; Molecular docking; Skin aging.

Fig. 1

Principal component analysis of the phytochemical profile of M. subulata hydrodistilled essential oils (HD), headspace aroma (HS) and supercritical fluid extracts (SF): (A) score plot and (B) loading plot with the contributing metabolites assigned

Fig. 2

Hierarchical cluster analysis (HCA)-derived dendrogram of M. subulata hydrodistilled essential oils (HD), headspace aroma (HS) and supercritical fluid extracts (SF) based on the phytochemical profile analyzed by GC/MS

Fig. 3

2D and 3D binding modes of 2-methyl hexacosane (A), behenic alcohol (B), EDTA (C), dl-α-Tocopherol (D) and 465C co-crystallized inhibitor (E) within the active sites of collagenase enzyme

Fig. 4

2D and 3D binding modes of N-(methoxysuccinyl)-Ala-Ala-Pro-Val-chloromethyl ketone (A) behenic alcohol (B) 2-methyl hexacosane (C) dl-α-tocopherol (D) within the active sites of elastase enzyme

Fig. 5

2D and 3D binding modes of isobutyl isobutyrate (A) isoamyl acetate (B) p-cymene (C) phytol (D) and kojic acid (E) within the active sites of tyrosinase enzyme