Optimization, Identification, and Quantification of Selected Phenolics in Three Underutilized Exotic Edible Fruits Using HPTLC

This study aimed to investigate selected bioactive components in three underutilized wild edible exotic fruits (Syzygium guineense Wild. DC, Ziziphus spina-christi L., and Citrus medica L.), using high-performance thin-layer chromatography and ultraviolet-visible spectrophotometry (HPTLC-UV-Vis), treated under three drying conditions. Ultrasound-assisted extraction was used to extract the target bioactive components under specified conditions, i.e., time of 15 min, temperature of 35 °C, methanol and water 75/25, v/v, and fruit powder-to-solvent ratio of 1:15, w/v. The mobile phase ratio for rutin, kaempferol, myricetin, and quercetin was toluene/ethylacetate/methanol/formic acid at 20:12:8:4, whereas, for phenolic acids, the ratio was 10:15:10:5, respectively. The HPTLC plates were scanned to identify and quantify selected compounds (phenolic acids, quercetin, rutin, myricetin, and kaempferol) at their maximum optimized absorption wavelengths. The contents of target bioactive components ranged from 0.64 ± 0.19 mg/100 g for rutin to 320.04 ± 7.10 mg/100 g for chlorogenic acid. Based on the results of this investigation, the phenol content of freeze-dried fruit was significantly (p ≤ 0.05) higher than other drying methods. The calculated average limit of detections and quantifications ranged from 0.37 to 75 ng/spot to 2.5 to 250 ng/spot, respectively. The average recoveries were 99.91 ± 5.65% for quercetin and 99.08 ± 5.96% for rutin. Overall, the validated HPTLC method was simple, selective, sensitive, and stable for the simultaneous identification and determination of phenolic acids and flavonoids. As a result, this study revealed that the contents of phenolic acids and flavonoids in selected exotic edible fruits can be used as effective antioxidants.