p - Coumaric acid exists in two forms trans - p - coumaric acid and cis - p - coumaric acid .
p - Coumaric acid is the most abundant isomer of the three in nature .
p - isomer   exists in two forms trans - p - coumaric acid and cis - p - coumaric acid .
p - Coumaric acid is the most abundant isomer of the three in nature .