Premna odorata: Seasonal Metabolic Variation in the Essential Oil Composition of Its Leaf and Verification of Its Anti-Ageing Potential via In Vitro Assays and Molecular Modelling

Abstract

The metabolic variation in the essential oil composition of Premna odorata leaves obtained from different seasons was quantitatively and qualitatively determined employing GC/MS (Gas Chromatography coupled with Mass Spectrometry) and GC/FID (Gas chromatography equipped with flame ionization detector) techniques. It displayed the existence of 97 constituents accounting for 94.19%, 92.27%, 91.95% and 92.63% for POS (spring), POM (summer), POA (autumn) and POW (winter) whole essential oils. β-Caryophyllene constituting the main metabolite in the oil in the different seasons. To better visualize the differences between them, GC data were exposed to chemometric analysis. A PCA (principal component analysis) score plot revealed the closeness of POS and POW. Molecular modelling on collagenase, elastase and hyaluronidase enzymes active centres shows that different compounds existing in the essential oil of Premna odorata leaves shows binding to the active sites with variable degrees that suggested its anti-ageing potential. Palmitic acid displayed the highest fitting for both the collagenase and elastase active centres in both pH-based and rule-based ionization methods with ∆G equals -78.27 and -44.77 kcal/mol, respectively; meanwhile, heptacosane showed the highest fitting score in the hyaluronidase centre with ∆G = -43.78 kcal/mol. In vitro assays consolidates the obtained modelling studies in which essential oil shows considerable anti-elastase and anti-hyaluronidase potential as evidenced by their IC₅₀ values being 49.3 and 37.7 μg/mL, respectively; meanwhile, the essential oil of Premna odorata leaves displayed mild anti-collagenase potential. Thus, it can be concluded that Premna odorata could serve as a promising anti-ageing naturally occurring drug that could be effectively incorporated by pharmaceutical industries in cosmetics combating ageing and skin wrinkling.

Keywords: GC/MS; Premna odorata; Verbenaceae; anti-ageing; essential oil; molecular modelling.

Figure 1

Gas Chromatography (GC) chromatograms of POS (A), POM (B), POA (C) and POW (D) using Rtx-5MS column.

Figure 2

Major constituents prevailing in essential oils of POS, POM, POA and POW.

Figure 3

Score plot (A) and loading plot (B) of GC data obtained from POS, POW, POM and POA essential oil analyses using PCA.

Figure 4

A heatmap comparison relied upon the abundance of individual components of P.O.S, P.O.M, P.O.A. and P.O.W; dark-red colour indicated non-detectable levels of the identified component.

Figure 5

2D and 3D binding modes of Palmitic acid (A) and epigallocatechin gallate (EGCG) (B) in the active sites of the collagenase enzyme.

Figure 6

2D and 3D binding modes of Palmitic acid (A) and EGCG (B) in the active sites of the elastase enzyme.

Figure 7

2D and 3D binding modes of Palmitic acid (A) and EGCG (B) in the active sites of the hyaluronidase enzyme.

Figure 8

In vitro anti-ageing potential of the essential oil of Premna odorata leaves (PO) using anti-collagenase, anti-elastase and anti-hyaluronidase versus EGCG.