A process for the extraction of the B group of vitamins from a first plant matter is disclosed wherein, prior to the said extraction operation, the first plant matter is treated with a second plant matter comprising acidic compounds. The acidification converts the vitamins into more water-soluble forms and increases the yield thereof. In one example, the first plant matter comprises guava fruit matter, holy basil leaves and lemon peels, the two last-mentioned plant species being the source of the acidic compounds. The vitamins extracted and the proportions thereof may be controlled by suitable choice of the plant species constituting the first and second plant matters and their quantities, such as to give a substantially ready formulation conforming to RDA values or other requirements. The vitamins extracted are B1, B2, B3, B5, B6 and B9, the above combination of plant matters giving a higher yield than others. The process is of general applicability to other plant constituents.