Fungistatic Activity of Floral Volatile Compounds of Alstonia scholaris

Abstract

Aims: The fragrant flowers of Alstonia scholaris are rich in volatile compounds or essential oils, which comprise terpenes such as 1,8-cineole and linalool. The effects of the oils on the growth of Aspergillus niger were assessed for the first time in the present study. Study Design: Fungal growth assay. Place and Duration of Study: Sample: Department of Botany, St. Xavier’s College, Mumbai, between September 2006 and December 2006. Methodology: The volatile compounds of A. scholaris were extracted through steam distillation and hydrodistillation by using a Clevenger apparatus. The effect of the steam distillate (10% v/v) on the number of spores of A. niger was observed over 5 days. Furthermore, three fractions with distinct fragrances and boiling points were collected through hydrodistillation. The effects of each fraction on mycelial growth and sporulation in A. niger were examined. Accordingly, each hydrodistilled fraction was incorporated in growth medium (10% v/v) inoculated with fungal spores. The growth of the fungus was observed over 5 days. Distilled water was used as the control. All experiments were conducted in triplicate. Results: The fungal samples treated with steam distillates showed a significantly lower number of spores than the control after 5 days (165 ± 36 vs. 35 ± 7 spores/mL) at P ≤ .05. Furthermore, the fungal samples treated with the hydrodistilled fractions exhibited a delayed mycelial growth and sporulation compared with the control over 5 days. Fraction 1 was most effective in delaying mycelial growth (Day 4 vs. Day 1). Notably, on Day 4 none of the treated samples but the control sample exhibited sporulation. Conclusion: The volatile compounds of A. scholaris flowers clearly suppressed and delayed both mycelial growth and sporulation in A. niger but did not inhibit growth entirely. Hence, the floral volatile compounds exhibit fungistatic activity against A. niger.