# Seasonal and Regional Effects on the Yield and Bioactive Constituents of Torreya nucifera Essential Oils in South Korea

## TL;DR

This study explores how seasons and regions in South Korea affect the yield and chemical composition of Torreya nucifera essential oil.

## Contribution

The study identifies optimal seasonal and regional conditions for maximizing yield and key bioactive compounds in Torreya nucifera essential oil.

## Key findings

- Oil yield was stable across seasons but varied significantly by region, with Hwasun showing the highest yield.
- D-limonene and 3-carene were identified as key chemical markers, with their levels influenced by season and region.
- Autumn harvest in Hwasun is optimal for maximizing both yield and D-limonene concentration.

## Abstract

The essential oil of Torreya nucifera, a coniferous tree native to East Asia, has notable bioactive properties with potential industrial applications. This study examined the effects of seasonal and regional factors on the yield and bioactive constituents of T. nucifera oils in South Korea. Leaf samples were collected in spring (March), summer (June), and autumn (September) of 2023–2024 from three ecologically distinct regions: Jeju Island, Jinju, and Hwasun. Oil yield was stable across seasons (0.9–1.6%) but varied significantly by region (p < 0.05), with Hwasun showing the highest yield. This stability across seasons may reflect the perennial evergreen nature of T. nucifera. Gas Chromatography-Mass Spectrometry (GC–MS) identified 32 volatile components, predominantly monoterpenes (83.7–90.4%) and sesquiterpenes (5.4–11.7%), with D-limonene and 3-carene as key chemical markers. Notably, 3-carene levels were significantly affected by region (p < 0.0001), with higher concentrations in Jeju oils, while D-limonene was influenced by season, region, and their interaction (p < 0.001), reaching peak levels in Hwasun during summer and autumn (up to 70%). Therefore, T. nucifera oil from Hwasun harvested in autumn can be optimised for commercial production by maximising oil yield and enhancing chemical markers.