Growth characteristics, optimal harvest timing, and quality assessment of three Evodia species cultivated in Japan

Immature Evodia fruits are used in herbal medicine for their analgesic properties; however, determining the appropriate time for harvesting these fruits remains challenging. Here, we investigated the growth characteristics and optimal timing for collecting the immature fruits of three Evodia species-E. rutaecarpa (Juss.) Benth., E. officinalis Dode, and E. hupehensis Dode-cultivated at the Tanegashima Division of the Research Center for Medicinal Plant Resources, Japan. Evodiamine and rutaecarpine content in the three species were measured across different collection seasons, and the relationship between time elapsed from the start of flowering and the levels of these active ingredients was determined. We found that the optimal time to collect the immature fruits of E. officinalis for use in herbal medicine was 2 weeks after flowering, when the fruit was heavier, contained more active ingredients, and had not yet dehisced. E. rutaecarpa fruits were heavier, contained more active ingredients, and retained their color (orange) until 3 weeks post-flowering. This suggests that the optimal collection time varied among species. Overall, E. rutaecarpa was the most suitable species for cultivation in Japan for use in herbal medicines because its optimal collection time was easier to determine, and its pericarp and seeds did not separate during drying. Therefore, to efficiently harvest Evodia fruits, cultivation methods should be optimized to leverage the specific growth characteristics of each species, with particular emphasis on accurately determining the optimal harvest time.