Candice Myrelle G. Lizada Niña Marie Y. Sedayon Fourth Year-Photon (March 2009)
Philippine Science High School Western Visayas Campus – Department of Science and Technology (DOST-PSHS WVC), Brgy. Bito-on, Jaro, Iloilo City 5000, Philippines
ABSTRACT
Fungal infections of Lagenidium sp. on mud crabs have long been a problem in crab aquaculture. Isatin is a chemical compound produced by Altermonas sp. which protects shrimp larvae from the same fungi. Isatin-intermediate compounds can also be found in indigo- producing plants such as Indigofera tinctoria. The antifungal property of this plant has not yet been studied.
This study explored the antifungal properties and the toxicity of the different concentrations (10,000ppm, 1,000ppm and 100ppm) of indigo leaf extracts and compared them with that of isatin and formalin.
Bath method was used in determining the antifungal activities of the different treatments. Fungal inhibition was measured in millimetres. The toxicity of the treatments was determined by percent mortality on crab larvae after 24 hours and 48 hours of exposure. Indigo extracts inhibited the growth of Lagenidium sp. (100.00±0.0000 and 2.5285+6.159152 for the 10,000ppm and 1,000ppm respectively). One-Way ANOVA and Fisher’s LSD showed that the 10,000ppm concentration significantly had the highest mean percent fungal inhibition on Lagenidium sp. (p=0.000, -0.05). Also, the same concentration of the extract exhibited the highest toxicity (10,000±0.0000) on crab larvae (p=0.005, -0.05) than the other treatments tested. Ten ppm formalin had the lowest toxicity (7.3333±3.5119) however. its percent fungal inhibition (5.9425±10.26029) is lower than that of the 10,000ppm.
The leaf extract of Indigofera tinctoria is a possible alternative for fungal infections in crabs. However, the crude extract is highly toxic to crab larvae. The antifungal property of the crude extract against Lagenidium sp. as well as its toxicity on crab larvae may be attributed to the isatin-intermediate compounds and other secondary plant metabolites present in it. Therefore, different fractions of the crude extract may be tested to determine which fraction will be lethal to the fungi, yet non-toxic to the crabs.