<em>Leptospermum scoparium</em> (Mānuka) and <em>Cryptomeria japonica</em> (Sugi) Leaf Essential Oil Seasonal Chemical Variation and Their Effect on Antimicrobial Activity

Abstract

This study evaluated the antimicrobial activity of Leptospermum scoparium (Mānuka) and Cryptomeria japonica (Sugi) essential oils and assessed the effect of seasonal chemical variation on the oils&amp;rsquo; antimicrobial efficacies. Plate based assays were conducted to elucidate the oils&amp;rsquo; spectrum of in vitro antimicrobial activity and to determine the oils&amp;rsquo; minimum inhibitory concentrations (MIC) as a measure of antimicrobial efficacy. Gas chromatography &amp;ndash; mass spectrometry was adopted to chemically profile oils distilled in different seasons. The resultant compositional information in conjunction with MIC data was used to evaluate the effect of seasonal variation on the oils&amp;rsquo; antimicrobial efficacy. Both Mānuka and Sugi essential oils were active against all classes of target microorganisms. However, limited activity was observed against Gram-negative bacteria. The oils displayed consistent chemotypic characteristics regardless of the time of distillation. Nonetheless, there were quantitative differences in compound abundance in both essential oils. Significant differences in the MIC of Sugi essential oil was observed against target microorganisms as a result of seasonal variation in constituent abundances while Mānuka essential oil&amp;rsquo;s antimicrobial efficacy was unaffected. This study demonstrates that seasonal chemical variation is an important quality assurance parameter to consider for future application of essential oils as antimicrobial agents in consumer products.

Variations in Essential Oil Chemical Composition and Biological Activities of Cryptomeria japonica (Thunb. ex L.f.) D. Don from Different Geographical Origins—A Critical Review

“…Such variation can be attributed to several factors, including exogenous (such as light, precipitation, growing region, nature of the soil and season) or/and endogenous factors (e.g., plant age, plant organ, developmental stage and genotype). Also, the EO yield can be influenced by these same parameters [27,[46][47][48] along with the extraction method used. However, there are conflicting reports in the literature about the influence of environmental conditions on C. japonica EO chemotypes, with some studies reporting no effects [33] and others [27] indicating that environmental factors strongly influenced the EO chemical profile.…”

Transcriptome and Metabolome Analyses Reveal Differences in Terpenoid and Flavonoid Biosynthesis in Cryptomeria fortunei Needles Across Different Seasons

“…Terpene content is affected by SCs (Merk et al, 1988). For example, in Japanese cedar (Cryptomeria japonica) (Bang et al, 2020), the maximum content of terpenes was observed in summer. Among most other conifers, such as white spruce (Pinus glauca) (von Rudloff, 1972), blue spruce (Pinus pungens) (von Rudloff, 1975), and Picea abies (Schnwitz et al, 1990;Kamaityt-Bukelskien et al, 2021), there is a similar seasonal pattern of variation in the number of terpenes.…”