Controlled-Release of Plant Volatiles: New Composite Materials of Porous Carbon-Citral and Their Fungicidal Activity against Exobasidium vexans

Abstract

Citral (Eo) exhibits excellent fungicidal activities. However, it is difficult to maintain long-term fungicidal activity due to its strong volatility. Herein, a controlled-release strategy by using biomass-derived porous carbon (BC) was developed to overcome the drawback of Eo. New composite materials were prepared by loading Eo on tea stem porous carbon (BC@Eo), and their controlled-release fungicidal activity against Exobasidium vexans was assessed. BC with a large specific surface area of 1001.6 m 2 /g and mesoporous structure was fabricated through carbonization temperature of 700°C. The BC@Eo materials were characterized using Fourier-transform infrared spectroscopy and X-ray powder diffraction. The results suggested that chemical and physical interactions occurred in BC@Eo. The Eo release profile suggested a biphasic pattern with an initial fast release on days 1-14 and a subsequent controlled phase on days 14-30. The in vitro cumulative release percentage of Eo from BC@Eo was 51% during one month, and this result was significantly lower than that from free Eo (cumulative release percentage of Eo of 82% in one week). The antifungal activities of Eo and BC@Eo against E. vexans were determined using the inhibition zone method. The results indicated that Eo and BC@Eo formed large inhibition zones of 19.66 ± 0.79 and 21.92 ± 0.77 mm, respectively. The influence on the hyphal structure of E. vexans was observed by scanning electron microscopy on day 30. The hyphal structure of E. vexans treated with BC@Eo was more shrunken than that treated with Eo at 30 days, suggesting that BC@Eo prolongs the fungicidal activity against E. vexans. This study demonstrated that the encapsulation of Eo in BC for developing the BC@Eo materials could be a promising strategy to inhibit volatility and maintain the fungicidal activity of Eo and provide a potential alternative for the reuse of abundant tea biomass waste resources.

A pH-Responsive Essential Oil Delivery System Based on Metal–organic Framework (ZIF-8) for Preventing Fungal Disease

“…In summary, the pH-responsive essential oil delivery system reported in this study can make a rapid feedback response to a stimulus signal (infection of pathogenic fungi), and quickly release the essential oil when it encounters its target with enhanced stability and inhibition. Compared with previous research results, − this delivery system not only improves the stability and efficacy of essential oil but also realizes the precise delivery of essential oil, which greatly improves the applicability of plant essential oil. This delivery system also provides a new strategy for sustainable plant disease management and precision farming.…”