Microencapsulation of Phenolic Compounds Extracted from Okra (Abelmoschus esculentus L.) Leaves, Fruits and Seeds

Several plants rich in phenolic compounds have many uses in the food and pharmaceutical fields. However, after extraction, these active biomolecules are susceptible to degradation. Microencapsulation is a possible solution to prevent this rapid degradation. In this study, phenolic compounds from the okra Abelmoschus esculentus L’s leaves, fruits and seeds were extracted using microwave-assisted extraction and then microencapsulated via the spray drying technique using maltodextrin combined with pectin (in a ratio of 10:1) as an encapsulation material. The total phenolic content, DPPH scavenging and antimicrobial activities of okra extracts and encapsulated samples were evaluated to verify the encapsulation efficiency. Particle size distribution determination and scanning electron microscopy of the microcapsules were also carried-out. The ethanolic leaf extract showed higher significant levels of total phenolic compounds (162.46 ± 4.48 mg GAE/g DW), and anti-oxidant (75.65%) and antibacterial activities compared to those of other aqueous and ethanolic extracts from fruits and seeds. Furthermore, the spray-dried ethanolic leaf extract had the highest total phenolic content. However, the encapsulated ethanolic fruit extract had the highest percentage of DPPH scavenging activity (30.36% ± 1.49). In addition, antibacterial activity measurements showed that the addition of ethanolic and aqueous seed microcapsules provided a significant zone of inhibition against the bacterium Brochotrix thermosphacta (38 mm and 30 mm, respectively). Okra aqueous leaf microcapsules showed the smallest Sauter mean diameter values (7.98 ± 0.12 µm). These data are applicable for expanding the use of okra leaves, fruits and seeds as food additives and/or preservatives in the food industry.