Novel sesquiterpenes and polyketides from the fungi Corynespora sp. YG-11 and Penicillium rubens YG-2 promote tobacco growth and enhance its stress resistance

The deterioration of tobacco ( Nicotiana tabacum L.) quality and yield is caused by abiotic stress (temperature, salt, heavy metals, etc.) and biotic stress (plant pathogens). The growth-promoting and stress resistance-enhancing compounds were isolated from endophytic fungi Corynespora sp . YG-11 and Penicillium rubens YG-2, both derived from tobacco tissue culture seedlings. One unprecedented sesquiterpene-cyclohexenone hybrid skeleton, corynecaserpene A ( 1 ), seventeen undescribed sesquiterpenes， corynecaserpenes B-R ( 2 - 18 ), a novel alkaloid, corynecapenoid A ( 19 ), and three known compounds ( 24 - 25 , and 29 ) from Corynespora sp. Four unreported polyketides, peniciruketides A-D ( 20 - 23 ), and three known compounds ( 26 - 28 ) from Penicillium rubens . The chemical structures were conclusively elucidated by spectroscopic analysis, ECD calculation, DP4 + analysis, Mosher’s method, and single-crystal X-ray diffraction (SXRD). The growth-promoting and stress resistance-enhancing activities of the compounds on tobacco seedlings were evaluated, and the results indicated that cyclohexenoneterpene F ( 27 ) exerted a significant growth-promoting effect on the shoot and root lengths of tobacco seedlings in the absence of stress. Corynecaserpene F ( 6 ) and fumiparaphine B ( 29 ) showed prominent stress-mitigating activity in tobacco seedlings under abiotic stresses (salt, low temperature), and corynecaserpenes B ( 2 ), J ( 10 ) and peniciruketide A ( 20 ) exhibited a significant alleviating effect on both abiotic stresses and biotic stress (plant pathogen) in tobacco seedlings. Additionally, cyclohexenoneterpene F ( 27 ) exhibited significant antifungal activity against Cladosporium sp., showing a mycelial growth inhibition rate of 68% at 30 μ g/mL. The structure-activity relationship of the compounds regarding their growth-promoting activity on tobacco seedlings were discussed. • Nineteen new compounds isolated from Corynespora sp., including a novel skeleton ( 1 ). • Four unreported polyketides ( 20 − 23 ) isolated from Penicillium rubens . • Compound 27 showed growth promoting effect in tobacco seedlings. • Compounds 2, 10 and 20 alleviated on abiotic/biotic stresses in tobacco seedlings.