Screening of phenolic compounds in australian grown grapes and their potential antioxidant activities

Grapes (Vitis Vinifera) are one of the world's most utilised and prized fruit. Grapes are a great source of antioxidants due to the abundance of phenolic compounds. Grape pulp is the main part of the grape being consumed. The pulp of five Australian grown grapes – Dawn Seedless (DS), Calmeria (CG), Golden Globe (GG), Menindee Seedless (MS), and Thompson Seedless (TS) will be qualitatively and quantitatively analysed for its phenolic composition and antioxidant capacity. The general trend followed: GG > TS > MS > DS > CG, and the phenolic content of the pulp also presented a significant positive correlation with the antioxidant capacity. GG revealing the highest levels of TPC (4.31 ± 0.11 mg GAE/g) and TFC (0.48 ± 0.09 mg QE/g) while TS were highest in TTC (0.94 ± 0.12 mg CE/g). Similarly, GG exhibited higher antioxidant capacity in DPPH (5.84 ± 0.17 mg AAE/g), FRAP (4.91 ± 0.14 mg AAE/g), and TAC (6.78 ± 0.12 mg AAE/g), while TS revealed highest radical scavenging ability for ABTS (4.56 ± 0.19 mg AAE/g). The LC-ESI-QTOF-MS/MS tentatively identified 78 phenolic compounds consisting of flavonoids (36), phenolic acids (31), lignans (3), stilbenes (1), and other polyphenols (7) in five grapes samples. Ten most abundant fruit-based targeted polyphenols were quantified. GG had a higher phenolic concentration in HPLC-PDA quantification, particularly for phenolic acids (gallic acid and chlorogenic acid) and flavonoids (kaempferol). Our study provides relatively adequate information on grape pulp's phenolic content and antioxidant capacity, providing confidence and research prospects to promote grape pulp use in different food, pharmaceutical and supplement industries, and even influencing grape cultivation.