Natural occurrence of moulds and mycotoxins in Synadenium glaucescens extracts (SGE) under different storage conditions

Abstract

Fungal growth and mycotoxin contamination in value-added medicinal plants products are quality and safety attributes that negatively affect entry to the market. This research aimed at investigating the occurrence of spoilage fungi and mycotoxins in Synadenium glaucescens extracts (SGE) from different plant parts and storage conditions. Laboratory whole water extraction method was used to prepare SGE from root-wood, root bark, leave, stem-bark and stem-wood. SGEs were subjected to storage temperature (25°C and 4°C refrigeration) and light (light and dark) conditions for 21 days. Samples were evaluated weekly to enumerate the occurrence of spoilage fungi and identified. In a follow-up experiment, pure cultures of Fusarium moniliforme and Aspergillus flavus were inoculated in SGEs and incubated for 14 days to allow production of mycotoxins. Aflatoxin and fumonisins were quantified using LC-MS/MS. It was established that 70% of samples of SGE contained Fusarium moniliforme and 60% Rhizopus spp. SGE samples stored under full light illumination were spoiled by Rhizopus species (35%), F. moniliforme (30%), F. pallidoroseum (3%), Cladosporium leguminicola (5%), C. sphaerospermum (2%), Alternaria alternate (6%) and Curvularia lunata (4%). The highest isolation frequency of F. moniliforme was in SGE from root wood (42%) and stem (42%). The highest (38%) isolation frequency of Rhizopus sp. was in SGEs from stem wood followed by root bark (32%) and 30% in both stem and root. Aflatoxin B1 was not detected in any sample. Fumonisin B1 (FB1) was detected in 80% of the samples and the concentration varied from 0.01μg/Kg to 6.33 μg/Kg. Among the samples contaminated with FB1, SGEs made from roots were contaminated by FB1 in a range of 0.03 to 0.04 μg/Kg, stem wood from 1.52 to 6.33 μg/Kg while in the root bark varied from 0.01 to 1.83 μg/Kg. SGE made from stem bark had FB1 ranging from 1.03 to 4.04 μg/Kg. Since fungal contamination was noted after 21 days of incubation, the source of spoilage fungi could be from the environment during postharvest handling. Therefore, it can be recommended that SGE safety can be ensured if good manufacturing practices (GMP) are maintained during preparation. Moreover, the Leaf SGEs were less vulnerable to fungal growth and fumonisin contamination at room temperature. Therefore, where the efficacy is the same, the leaf of S. glaucescens is possibly a better source of SGE formulations. These findings provide a benchmark of future investigations for more innovative GMP and safety measures to protect consumers against risks of exposure to mycotoxins.