Bioactive Components And Antioxidant Capacity Of Loquat (Eriobotrya Japonica Lindl.) Flower And Fruit

Bioactive compounds such as carotenoids,oleanolic acid(OA),ursolic acid (UA),amygdalin,flavonoids and phenolics were identified and quatified in the loquat (Eriobotrya japonica Lindl.)flower and fruit of different cultivars.The effects of different tissues and developmental stages on the contents of these bioactive components were studied.Moreover,the antioxidant capacity of flower and fruit extract and their relationship with the content of bioactive compounds were analyzed in the present study.The main results were as followings:By using HPLC system coupled with a photodiode array(PDA)detector and a C₃₀reversed phase column,15 carotenoids were detected in the saponified extraction of loquat flower(cv.Ruantiaobaisha),seven of which were identified.Lutein was the most abundant carotenoids in the flower,accouting for 35.19%of total carotenoids. The average content of lutein and total colored carotenoids in loquat flower from five cultivars were 10.11±1.25 and 24.25±3.00μg/g DW,respectively,where Ruantiaobaisha,Dahongpao,Baozhu,Dayeyangdun showed no significant difference between each other,while the flower of Jiajiao loquat contained significant lower amount of lutein and total carotenoids compared with the other four cultivars.The content of lutein and total carotenoids in the different tissues of loquat flower varied greatly,where pistil and stamen had the highest while petal contained the lowest lutein and total colored carotenoids content.Loquat fruits of 24 different cultivars were analyzed for peel color,carotenoid content and provitamin A values.Compared with white-fleshed cultivars,red-fleshed cultivars had higher a^* values,lower lightness(L^*)and b^* values,and higher the ratio of a^*/b^* and lower hue angle(H°)accordingly.In total,23 carotenoids in loquat fruits of Ruantiaobaisha and Dahongpao were detected,10 of which were identified.β-Carotene and lutein were the major earotenoids in peel,which in total accounted for about 60%of total colored carotenoids in both red-and white-fleshed cultivars.β-cryptoxanthin,and in some red-fleshed cultivars,β-carotene,were the most abundant carotenoids in flesh,and in total they accounted for over half of the colored carotenoids.On average,1.3-and 11.1-fold higher levels of colored carotenoids were observed in peel and flesh tissue of red-fleshed cultivars,respectively.Correlations analysis suggested that the total content of colored carotenoids positively correlated with a^* and ratio of a^*/b^*,while it negatively correlated with L^*,b^* and H°.The average vitamin A values,as retinol equivalents(RE),were 0.49 and 8.69μg/g DW (8.46 and 135.17μg/100 g FW)for of loquat flesh of white-and red-fleshed cultivars, respectively.The carotenoid content in the peel of both Ruantiaobaisha and Dayeyangdun experienced a decrease followed by an increase during the fruit development.As the peel color changed from green to yellow,lutein decreased whileβ-carotene increased significantly.In loquat flesh,similar changes took place in the early developmental stages of both cultivars,however,the carotenoid metabolism differed greatly during the late developmental stages.Total colored carotenoid in Ruantiaobaisha kept decreasing and a slight increase was found at the ripening stage,while the initial decrease in total colored carotenoid in Dayeyangdun was followed by a dramatic accumulation ofβ-cryptoxanthin andβ-carotene in the ripening fruit.The simple and accurate methods for determination of OA,UA and amygdalin were developed by HPLC coupled with a C₁₈reversed phase column and a UV/Vis detector.All three compounds were detected at 210 nm with a flow rate of 1.0 mL/min. The mobile phase consisted of methanol(A)and 0.03 mol/L phosphate buffer(pH 2.8) (B)with a ratio of 88:12(A:B,v/v)for simultaneous detection of OA and UA,and 25:75(A:B,v/v)for detection of amygdalin.The established methods showed good precision and accuracy with overall intra-day and inter-day variation of 0.99-3.55% and 1.05-4.05%,respectively,and overall recoveries of 97.37-99.32%for the three compounds.These above methods were applied to determine the OA,UA,and amygdalin content in loquat flower and fruit of different cultivars and different tissues. Results showed that cultivar had minor effect on the content of all three compounds in the flower.However,different developmental stages and flower tissues showed significant effect on the contents of all three bioactive components in the flower,stageâ…£and sepal contained highest OA and UA content,while stageâ…¢and petal had highest amygdalin content.The contents of OA,UA,and amygdalin varied with tissues in loquat fruit.Peel contained highest OA and UA content,while amygdalin was mainly founded in the kernel.The differences of OA and UA content in peel and amygdalin content in kernel between different cultivars were evident.The average content of flavonoids and phenolics in loquat flower of five cultivars were 1.81±0.07 and 9.15±0.20 mg/g DW,respectively.The content of flavonoids and total phenolics in different developmental stages and different tissues of flower differed significantly,with the highest flavonoids and phenolics content in stageâ…¢and petal,respectively.Antioxidant capacity,analyzed by FRAP,DPPH and ABTS,showed high correlation with the content of flavonoids and phenolics,with the highest correlation coefficient of 0.886^**and 0.973^**gotten by ABTS.The main antioxidant capacity in loquat flesh was hydrophilic,and it accounted for 89.33-95.67%of total antioxidant capacity.Our results also showed that 50.95-91.16%of the hydrophilic antioxidant capacity was contributed by phenolics, indicating that phenolics is important antioxidant in loquat.Lipophilic antioxidant capacity only accounted for 4.33-10.67%of the total antioxidant capacity.Lipophilic phenolics,carotenoids as well as other lipophilic compounds in loquat flesh may contribute greatly this part of antioxidant capacity.