ABSTRACT
Currently, the search of novel phytochemicals with unique biological potentialities is a pre-requisite for the designing ideal drugs for the human kind. Sea weeds are bioresources with a broad spectrum of medicinal properties with minimal side effects. Kerala, the Southern state of India reported high incidence of Chikungunya virus (CHIKV) infections in the last several tears. No specific virucidal therapy or effective vaccines are available. This emphasizes the need of searching for phytochemicals as drugs with less cost and more effective. Therefore, an attempt was made in screening purified terpenoid extracts of selected sea weeds as anti-CHIKV potential. In this study the terpenoids composition from the red algae Hypnea musciformis, Kappaphycus alvarezii and Gracillaria dura were identified and analyzed by thin layer chromatography and Gas chromatography- Mass spectrum. The methanolic extract of seaweeds was purified by column chromatography and each fraction was eluted by using petroleum ether and ethyl acetate as solvent combination. The analysis of the purified fraction of H. musciformis and K. alvarezii revealed the presence of 8 terpenoid fractions, and G. dura showed only 4 major components respectively. Vero cell lines were employed in the antiviral assays, infected to CHIKV, and treated with varied doses of purified terpenoid extracts. In the antiviral activity, terpenoid extracts of G. dura showed remarkable and promising EC50 inhibitory effect at 1.25 μg/ml. Further, the terpenoid extracts displayed efficient virucidal activity against CHIKV (inhibit around 90%) with 5 μg/ml dosage. As the last phase, terpenoid extracts added at time intervals of 0, 1, 2, 3 post-infection periods still maintained a significant inhibitory potential against CHIKV viral replication. Thus, the overall study suggests that the terpenoid extracts of G. dura may be effectively used in the prevention and treatment of CHIKV infections. Clinical studies may be warranted for designing a promising new anti-CHIKV drug.
ABSTRACT
Alternaria leaf spot disease is a major threat to sesame (Sesamum orientale L.) caused by Alternari asesami. Induced resistance is an alternative to systemic disease resistance response of plants. The present study aims to evaluate Trichoderma species efficacy as biocontrol via induction of resistance against A. sesami in sesame species. During in vitro bio control test, T. harzianum colonize and parallely inhibit the growth of the fungal pathogen. Expression of various defence related enzymes observed in sesame induce resistance against the pathogen infection in the host. T. harzianum coupled with inoculation of A. sesami enhance the remarkable induction of defence enzyme such as peroxidase (POX), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) and also the phenolic content compared with the control. The enzyme activity increased from 48 h of sampling and peaked at 72 h and then decreased after 72 h. In greenhouse and field experiments, soil treatment with a powder formulation of T. harzianum two weeks before planting or at the time of planting reduced significantly the incidence of diseases on both the wild and cultivar Thilarani.The results demonstrate that T. harzianumcan be successfully applied as a biological control against Alternaria leaf spot disease in sesame.
ABSTRACT
Alternaria sesami causes leaf spot disease in Sesamum orientale. Conidium germination, inoculation, penetration and colonization of the pathogen on the plant surfaces were studied using scanning electron microscopy. Electron microscopy analysis revealed multiple germ tubes from conidium that spread in all direction across the leaf surfaces. Penetration in the plant surface occured, directly through the epidermis or via stomata with or without the appressoria formation. Hyphal penetration continued through the substomata cavity and some of hyphal branches grew in the intercellular space of mesophyll tissue. Hyphal toxin, caused cell and cell wall damages. Changes in different biochemical parameters in the diseased sesame plants (both in wild and cultivar) were compared to control. Transmission electron microscopy showed structural changes in the chloroplast of diseased plants. Isozyme pattern and assays of different enzymes, namely catalase, acid phosphatase and peroxidase expressed varied level of activities. Meanwhile, esterase, polyphenol oxidase and superoxide dismutase in diseased plants showed remarkable levels compared to control. Due to the infection, chlorophyll content, carbohydrates and total soluble protein decreased whereas free amino acid, proline, phenols and disease-related proteins increased in the host plants. Differential SDS-PAGE band profiling of total soluble proteins were also observed in plants due to the infection.