Composition and Antimicrobial Activities of Secondary Metabolites in Tomato and Strawberry Plants

Abstract

This thesis is consisted of Part I and II in tomato and strawberry researches, respectively. Chapter I and III deal with the secondary metabolites profiling and Chapter II and IV deal with antimicrobial activity of extracts from various parts of tomato and strawberry plants, respectively. In Chapter I, contents of carotenoids, phenolics, volatile organic compounds, and alkaloids in leaves, intermodal stems, fruits, and roots of Bacchus tomato at different developmental stages were measured. Lycopene content in red fruits was 196.2 g·g-1 FW. -Carotene and lutein contents in the 24th leaves were 23.2 and 25.6 g·g-1 FW, respectively, and were greater than those in the other parts. Content of chlorogenic acid in the 18th leaves was 40.1 g·g-1 FW, while that in the other parts was lower than 31.0 g·g-1 FW. Contents of caffeic and vanillic acids in the 24th leaves were 9.2 and 1.6 g·g-1 FW, respectively, and were greater than those in the other parts. Moreover, younger leaves contained more diverse volatile organic compounds including mono- and sesquiterpenes. Contents of dehydro- and -tomatine were greatest in leaves, followed by internodal stems, roots, and fruits. Younger leaves and internodal stems contained more dehydro- and -tomatine than older leaves and internodal stems. Contents of dehydro- and -tomatine in the 24th leaves were 889.1 and 1,417.9 g·g-1 FW, respectively, and were greatest among all parts tested. These results indicated that, except lycopene, tomato leaves contained greater secondary metabolites than red fruits. In Chapter II, antimicrobial activity was confirmed in methanol, acetone, dichloromethane, and hexane extracts from various parts of Bacchus tomato plants including non-edible parts. Minimum inhibitory concentration of actetonic extract from tomato leaves on Fusarium oxyspourum f. sp. lycopersici, Colletotrichum coccodes, Phytophthora capsici, Rhizoctonia solani, and Glomerella cingulata was lowest. The actetonic extracts also reduced the mycelial growth of F. oxysporum f. sp. lycopersici and R. solani. Mycelial growth of R. solani, especially, was significantly inhibited by the actetonic extracts. Bioautography on thin layer chromatography showed that the acetonic extract included two antimicrobial compounds against R. solani. The dominant antimicrobial compounds in the chromatogram were linolenic and caffeic acids. Linolenic acid had greater inhibitory effect on mycelial growth of R. solani than caffeic acid. In Chapter III, a comparative chemical analysis was performed on the compounds found in roots, leaves, petioles, runners, and green and red fruits during vegetative propagation and reproductive growth of Seolhyang strawberry. Contents of ellagic and gallic acids in leaves of runner plants during vegetative propagation were 7.4 and 5.1 mg·g-1 FW, respectively, and were higher than those in the other parts. The main volatile organic compound was identified as 3-hexen-1-ol, and it was detected mostly in leaf parts. Content of ellagic acid in leaves during reproductive growth was 13.0 mg·g-1 FW, while that in the other parts was below 6 mg·g-1 FW. Content of gallic acid in green fruits was 2.8 mg·g-1 FW and was higher than that in the other parts. Red fruits contained the most diverse volatile organic compounds, including sesquiterpenes, among the tested plant parts but contained the lowest contents of ellagic and gallic acids. In Chapter IV, antimicrobial activity was confirmed in methanol, acetone, dichloromethane, and hexane extracts from various parts of Seolhyang strawberry plants including non-edible parts. Minimum inhibitory concentration value of methanolic extract from strawberry leaves was lowest on all tested microorganisms (Fusarium oxyspourum f. sp. lycopersici, Colletotrichum coccodes, Phytophthora capsici, Rhizoctonia solani, Glomerella cingulate, and Phytophthora cactorum). The methanolic extracts also inhibited the mycelial growth of R. solani, G. cingulate, and C. coccodes. Mycelial growth of C. coccodes, especially, was significantly inhibited by the methanolic extracts. Moreover, the methanolic extracts inhibited mycelial growth of the other Colletotrichum spp. such as C. caudatum, C. higginsianum, C. liliacearum, C. lindemuthianum, C. musae, C. orbiculare, and C. truncatum. Bioautography on thin layer chromatography showed that the methanolic extract included two antimicrobial compounds against C. coccodes. The dominant antimicrobial compounds in the chromatogram were tyrosol and -sitosterol. Tyrosol showed greater inhibitory effect on mycelial growth of C. coccodes than -sitosterol. In conclusion, non-edible parts of tomato and strawberry, especially leaves, contained greater secondary metabolites contents than edible parts and contained antimicrobial compounds against phytopathogenic microorganisms. The results could be a useful database for utilizing of the non-edible parts which were dumped after last harvest and could provide information for developing natural antimicrobial agents against phytopathogens.