Vitamin B6 is a common name for six different water - soluble compounds that are present in foods and in the body, of which pyridoxal phosphate (PLP) is the most common form (over 60 % of the body's vitamin B6 is PLP). (journals.plos.org)
Plant foods contain pyridoxine, while animal foods contain a mix of pyridoxal and pyridoxamine. (westonaprice.org)
There could be additional contributing factors to why they saw no improvement, such as other nutrient deficiencies or a difficulty in converting vitamin B6 into its active form pyridoxal -5-phosphate. (natural-fertility-info.com)