Bioassay-guided isolation studies on the extracts of yellow flowers of Tagetes patula L. against the Heterodera zeae were carried out to identify phytochemicals lethal to this economically important cyst nematode. In vitro investigation of a polar extract and fractions showing activity led to the isolation of phenolic compounds (flavonoids and phenolic acids). In the nonpolar extract, a few fatty acids, their methyl esters, and thiophenes (including α-terthienyl) were detected. In studies of compounds obtained commercially, α-terthienyl and gallic and linoleic acids showed 100% mortality at concentrations of 0.125% after 24 h. Assessment of structure-activity relationships revealed that an increase in the number of hydroxyl groups in phenolic acids increased the activity; with fatty acids, activity depended on chain length and the number and position of double bonds. Crude extracts of the flowers of different colors also have promising activity.

These findings demonstrate that the plant polar extracts and fractions possess significant antioxidant property with non-toxic effect. Compound 1 is a genuine plant constituent of T. patula.

The current study evaluates the antibacterial and antifungal activities of extracts from different parts of Tagetes patula Linn. (Asteraceae), reported for the first time in a single set of experiments. In the preliminary assay, the methanol extract of the flower (JFM) was found to possess antimicrobial activity against a number of bacteria with inhibition zone diameters ranging from 9 to 20 mm, the bioassay-guided fractionation of which led to the isolation of a flavonoid patuletin (3) in high yield as the active antibacterial principle with minimum inhibitory concentration (MIC) value of 12.5 µg/disk against Corynebacterium spp., Staphylococcus spp., Streptococcus spp., and Micrococcus luteus. Its glucoside, patulitrin (4), was found to be weakly active, except against Staphylococcus saprophyticus, Streptococcus fecalis, and Streptococcus pyogenes with inhibition zone diameters of 11, 16, and 12 mm, respectively. The cinnamate derivative (3b) of 3 showed antibacterial activity comparable with the parent flavonoid with a MIC value of 50 µg/disk against Corynebacterium spp., whereas benzoate derivative (3a) was found to be devoid of any activity; both the derivatives are new compounds. Moreover, the longchain alcohol 5, which displayed antibacterial activity in the preliminary testing, was obtained in large quantity directly from the petroleum ether extract of the involucre of the flowers.