Analysis of nutritional quality and antioxidant activity of male flowers in walnut

Abstract：【Objective】In order to utilize the abundant resources of male flowers of walnut (Juglans re⁃gia), nutritional quality and antioxidant activity of the male flowers of five different genotypes were evalu⁃ated.【Methods】The male flowers of‘Qianhe-5’‘Qianhe-7’‘Qianhe-8’‘Caishen-10’and‘Xiangling’were collected from Hezhang county of Bijie city, Guizhou province. The content of crude protein was de⁃termined by semi micro Kjeldahl method, the content of fat by Soxhlet extraction, the content of solublesugar by anthrone colorimetric method, titratable acid content by acid hydrolysis method, the content ofstarch, crude fibre and ash by acid hydrolysis, weighing and furnace method, separately. The content ofmineral elements was measured by atomic absorption spectrophotometer. Determination of amino acids byautomatic amino acid analyzer, the ascorbic acid by high performance liquid chromatography (HPLC), to⁃tal phenol content by Folin Shaw colorimetry, total flavonoids content by aluminum nitrate colorimetricmethod, DPPH free radical scavenging test was carried out with reference to the method described by Mo⁃tamed, FRAP iron ion reduction test with reference to the method described by Hatamnia. The varianceanalysis and correlation analysis were carried out using DPS v7.05 software. The multiple comparisonswere performed using the Duncan’s new bipolar difference method.【Results】There were significant differ⁃ences in the contents of the normal nutritional components of male flowers among the different genotypesof walnut. All conventional nutrients except for dry matter had some differences, the content of total solu⁃ble sugar and starch had the highest difference. The order of the total soluble sugar content was‘Qianhe5’>‘Qianhe-7’>‘Qianhe-8’>‘Xiangling’>‘Caishen-10’and the order of the starch was‘Qianhe-8’>‘Qianhe-7’>‘Xiangling’>‘Qianhe-5’>‘Caishen-10’. The conventional nutrient content of themale flowers of walnuts originated from Guizhou were higher than that of‘Xiangling’introduced from theNorth of China. Among four local varieties,‘Qianhe-7’was more prominent, especially in protein, carbo⁃hydrates and available.‘Caishen-10’was inferior to other three varieties in total soluble sugars, starchand carbohydrates.‘Qianhe-8’had the highest starch content and‘Qianhe-5’had the highest crude fi⁃ber content.‘Qianhe-8’and‘Qianhe-5’did not have advantage in other seven nutritional components.‘Xiangling’had the lowest contents of Fe, Mn, Cu, B and the highest content of Zn.‘Qianhe-7’had thehighest total content of macroelements and microelements especially P, Fe, Mn, Cu.‘Qianhe-5’, had thelowest total content of macroelement especially K, and Zn and B, and the highest content of microelements.‘Qianhe-8’and‘Qianhe-10’had no advantages in total mineral elements, particularly in P andCa. The male flowers of different genotypes of walnut were rich in 17 kinds of amino acids and 9 kinds ofessential amino acids (including semi essential amino acids Arg and His). There was no significant differencein the total amount of amino acids (10.10-11.01 g·100 g^-1) and essential amino acids (4.11-4.54 g·100 g^-1) inthe male flowers of different walnut although the essential amino acid/total amino acid (EAA/TAA) of‘Xiangling’was lower than 40%.‘Qianhe-7’had highest contents of Asp, Ala, Tyr and‘Qianhe-8’hadthe highest content of Gly than that of other two local varieties.‘Qianhe-5’had the lowest contents ofAsp, Gly, Tyr, His, Lys and Arg, and the highest content of Pro. The order of content of ascorbic acid was‘Qianhe-5’>‘Qianhe-7’>‘Qianhe-8’>‘Caishen-10’>‘Xiangling’. The order of the content of total phenols and total flavonoid was‘Qianhe-8’>‘Xiangling’>‘Qianhe-7’>‘Caishen-10’>‘Qianhe-5’. And the order of antioxidant activity was the same as total phenols and total flavonoid.【Conclusion】There was no significant difference in the nutritional composition of the male flowers of the different wal⁃nuts, while there was difference in the contents of the nutritional components. The local varieties especial⁃ly‘Qianhe-7’had high previlege in the nutritional quality compared with‘Xiangling’originated fromthe North of China.