Insect Growth Regulator (IGR) effects of Eucalyptus citriodora Hook (Myrtaceae) / Efectos tóxicos e IGR de Eucalyptus citriodora Hook (Myrtaceae)

In addition to eucalyptin the methanol extract from leaves of Eucalyptus citriodora (Myrtaceae) afforded the known compounds apigenin, chrysin, luteolin, naringenin, quercetin; together with betulinic acid, oleanolic, ursolic acid, and two remaining complex mixtures of unidentified flavonoids and triterpenes. These compounds together with triterpenes mixtures, hexane and ethyl acetate extracts showed antifeedant, insecticidal and insect growth regulatory activities against fall armyworm [Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae)] an important pest of corn, and yellow mealworm [Tenebrio molitor (Coleoptera:Tenebrionidae)] a pest of stored grains. The most active compounds were chrysin, eucalyptin, quercetin, luteolin, and betulinic and oleanolic acids and the mixtures of flavonoids and triterpenes (M1 and M2). These compounds and mixtures had IGR activity between 0.2 to 5.0 ug/mL and insecticidal effects between 5.0 and 10.0 μg/mL.The extracts were insecticidal to larvae, with lethal doses between 20-100 ug/mL. These compounds appear to have selective effects on the pre-emergence metabolism of the Lepidoptera, since in all treatments of the larvae of S. frugiperda the pupation was shortened and this process showed precociousness in relation to control. Thus, these substances may be useful as potential natural insecticidal agents.

Extracto metanolico de hojas de Eucalyptus citriodora (Myrtaceae) proporcionó además de eucalyptin, flavonoides tales como apigenina, crisina, luteolina, naringenina, quercetina; los triterpenos, ácido oleanólico, ácido ursólico betulínico, y dos mezclas complejas de flavonoides y triterpenos no identificados M1 y M2. Los flavonoides, triterpenos y mezclas de triterpenos, extractos de acetato de etilo y hexano mostraron efectos antialimentarios, insecticida y actividad reguladora de crecimiento (IGR) frente al gusano cogollero [Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae)], una plaga importante del maíz y frente al gusano de la harina [Tenebrio molitor (Coleoptera: Tenebrionidae)], una plaga de los granos almacenados. Los compuestos más activos fueron crisina, eucalyptin, quercetina, luteolina, ácido betulínico y ácido oleanólico y las mezclas de flavonoides y triterpenos (M1 y M2). Estos compuestos y mezclas mostraron actividad IGR entre 0,2 y 5,0 ug/mL y efectos insecticidas entre 5,0 y 10,0 μg/mL. Los extractos mostraron carácter insecticida para las larvas a dosis letales entre 20-100 ug/mL. Estas muestras parecen tener efectos selectivos sobre el metabolismo de pre-emergencia de los lepidópteros, ya que en todos los tratamientos de las larvas de S. frugiperda el tiempo de la pupación se acortó; este proceso muestra precocidad en relación con el control, las substancias ensayadas en este trabajo pueden ser útiles como potenciales agentes insecticidas naturales.

Antifungal and antibacterial activities of Mexican tarragon (Tagetes lucida).

Mexican tarragon (Tagetes lucida Cv. Asteraceae: Campanulatae) is an important, nutritious plant and an effective herbal medicine. Seven coumarins, 7,8-dihydroxycoumarin (4), umbelliferone (7-hydroxycoumarin) (5), scoparone (6,7-dimethoxycoumarin) (7), esculetin (6,7-dihydroxycoumarin) (11), 6-hydroxy-7-methoxycoumarin (12), herniarin (7-methoxycoumarin) (13), and scopoletin (6-methoxy-7-hydroxycoumarin) (14), and three flavonoids, patuletin (18), quercetin (19), and quercetagetin (20), were isolated from CH2Cl2 and MeOH extracts from aerial parts of T. lucida. In addition, 6,7-diacetoxy coumarin (15), 6-methoxy-7-acetylcoumarin (16), and 6-acetoxy-7-methoxycoumarin (17) derivatives were synthesized. 8-Methoxypsoralen (1), 8-acetyl-7-hydroxycoumarin (2), 7,8-dihydroxy-6-meth-oxycoumarin (3), 6,7-dimethoxy-4-methylcoumarin (6), 5,7-dihydroxy-4-methylcoumarin (8), 4-hydroxycoumarin (9), 4-hydroxy-6,7-dimethylcoumarin (10), naringenin (21), glycoside-7-rhamnonaringin (22), and rutin (23) were commercially obtained (Sigma-Aldrich). All of these compounds and extracts (M1 and M2) were assayed against bacteria and fungi. The antibacterial activity was determined on Bacillus subtilis, Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Salmonella typhi, Salmonella sp., Shigella boydii, Shigella sp., Enterobacter aerogenes, Enterobacter agglomerans, Sarcina lutea, Staphylococcus epidermidis, Staphylococcus aureus, Yersinia enterolitica, Vibrio cholerae (three El Tor strains, CDC-V12, clinic case, and INDRE-206, were obtained from contaminated water), and V. cholerae (NO-O1). The evaluated fungi were Aspergillus niger, Penicillium notatum, Fusarium moniliforme, Fusarium sporotrichum, Rhizoctonia solani, and Trichophyton mentagrophytes. The most active compounds against Gram-positive and -negative bacteria were the dihydroxylated coumarins 3 and 4. In addition, 2-4, 6, 7, and 11 showed an interesting activity against V. cholerae, a key bacterium in the contaminated water; 2-4 were the most active. Coumarins were the most effective compounds against Gram-negative bacteria. The extract MeOH/CH2Cl2 (1: 4) M2 at 0.4 microg/disk inhibited the growth of E. coli and P. mirabilis (40%), K. pneumoniae (31.1%), Salmonella sp. (35.5%), and Shigella sp. (0%) at 72 h of culture. The dimethoxy compounds 6 and 7 showed a strong activity against fungal strains, especially T. mentagrophytes and R. solani (100% of inhibition at 125.0 and 250.0 microg/mL, respectively).