Diterpenoids with herbicidal and antifungal activities from hulls of rice (Oryza sativa)

Authors: GU, CHENG-ZHEN - Fujian Agriculture And Forest University; XIA, XIAO-MEI - Fujian Agriculture And Forest University; LV, JING - Fujian Agriculture And Forest University; TAN, JIAN-WEN - South China Botanical Garden; Baerson, Scott; Pan, Zhiqiang - Peter; SONG, YUAN-YUAN - Fujian Agriculture And Forest University; ZENG, REN-SEN - Fujian Agriculture And Forest University

Submitted to: Fitoterapia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2019
Publication Date: 5/28/2019
Citation: Gu, C., Xia, X., Lv, J., Tan, J., Baerson, S.R., Pan, Z., Song, Y., Zeng, R. 2019. Diterpenoids with herbicidal and antifungal activities from hulls of rice (Oryza sativa). Fitoterapia. 136:104183. https://doi.org/10.1016/j.fitote.2019.104183.
DOI: https://doi.org/10.1016/j.fitote.2019.104183

Interpretive Summary: Higher plants produce a diversity of specialized compounds, sometimes referred to as ‘secondary metabolites’, which typically play roles in protecting plants against various environmental and biological stressors. Two important roles played by these specialized metabolites are defense against pathogenic fungi and in plant-plant competition (allelopathy). Secondary metabolites playing a role in plant-plant competition are referred to as allelochemicals. Secondary metabolites often accumulate within specific plant organs, and insight into their biological roles can often be obtained by studying their accumulation patterns. In this work we’ve identified a series of compounds accumulating specifically within the seed hulls of rice, which possess both antifungal and allelochemical activities. These compounds were tested against the agriculturally important fungal pathogens Magnaporthe grisea, Rhizoctonia solani, Blumeria graminearum and Fusarium oxysporum and were found to significantly inhibit their growth in in vitro studies. In addition, the same compounds were also found to significantly inhibit the growth of Echinochloa crusgalli (barnyardgrass), an important weed species found throughout the Americas, Asia, and Africa. Thus, this study provides new information contributing to the understanding of the chemical defenses employed by Oryza sativa, one of the world’s most important crop species.

Technical Abstract: Diterpenoids are the main secondary metabolites of plants and with a range of biological activities. In the present study, 7 compounds were isolated from the hulls of rice (Oryza sativa L.). Among them, 3 diterpenoids are new namely, 3,20-epoxy-3a-hydroxy- 8,11,13-abietatrie-7-one (1), 4,6-epoxy-3ß-hydroxy-9ß-pimara-7,15-diene (2) and 2-((E)-3- (4-hydroxy-3-methoxyphenyl) allylidene) momilactone A (3). While, 4 terpenoids are known, namely momilactone A (4), momilactone B (5), ent-7-oxo-kaur-15-en-18-oic acid (6) and orizaterpenoid (7). The structures of these diterpenoids were elucidated using 1D and 2D NMR in combination with ESI-MS and HR-EIMS. Furthermore, all isolated compounds displayed antifungal activities against four crop pathogenic fungi Magnaporthe grisea, Rhizoctonia solani, Blumeria graminearum and Fusarium oxysporum, and phytotoxicity against paddy weed Echinochloa crusgalli. The results suggested that rice could produce a variety of secondary metabolites to defend against weeds and pathogens.