In this study, researchers at Tongji University identified the presence of microRNAs in coconut water by real-time PCR based on the results of high-throughput small RNA sequencing. In addition, the differences in microRNA content between immature and mature coconut water were compared. A total of 47 known microRNAs belonging to 25 families and 14 new microRNAs were identified in coconut endosperm. Through analysis using a target gene prediction software, potential microRNA target genes were identified in the human genome. Real-time PCR showed that the level of most microRNAs was higher in mature coconut water than in immature coconut water. Then, exosome-like nanoparticles were isolated from coconut water. After ultracentrifugation, some particle structures were seen in coconut water samples by using DiI fluorescence staining. Subsequent SEM observation and DLS analysis also revealed some exosome-like nanoparticles in coconut water, and the mean diameters of the particles detected by the two methods were 13.16 nm and 59.72 nm, respectively. In conclusion, there are extracellular microRNAs in coconut water, and their levels are higher in mature coconut water than in immature coconut water. Some exosome-like nanoparticles were isolated from coconut water, and the diameter of these particles was smaller than that of animal-derived exosomes.
DLS and SEM results
(A and B) SEM observations of nanostructures in coconut water at magnifications of 90 000 and 110 000. The average particle size was 13.45 ± 2.21 and 11.66 ± 1.10, respectively. (C and D) SEM observations of nanostructures in milk at magnifications of 90 000 and 100 000. The average particle size was 30.83 ± 6.19 and 29.54 ± 5.13, respectively. (E) DLS observation of nanostructures in coconut water and milk. The average size of particles in coconut water was 59.72 nm, and the average size of particles in milk was 100.40 nm. SEM results were analyzed using ImageJ to calculate the average particle size. DLS results were obtained from the instrument display. Data are represented as the average ± standard error.