Cultivation protocol using a coir-based substrate modulates the concentration ofbioactive compounds and the antioxidant activity of Passiflora alata Curtis seedlings

The use of coconut coir dust is a low-cost cultivation practice. Thus, this study aimed to determine the effect of coconut coir dust proportion on foliar secondary metabolite biosynthesis and growth of Passiflora alata Curtis (sweet passion fruit). This Passiflora species possess pharmaceutical relevance and the use of organic-based substrates may promote the production of bioactive compounds in the phytomass. An experiment in a greenhouse was set up with three proportions of coir dust mixed with a commercial substrate for seedlings (CSS) (peat-based) (S1= 1:1:1, CSS: sand: coconut coir dust; S2= 1.5:1.5:1, CSS: sand: coconut coir dust and S3= 1:1, sand: CSS) in seven replicates. After 68 days, growth parameters were measured (height, leaf area, number of leaves, stem diameter, and dry matter), and the harvested leaves were used to prepare ethanolic extracts. The total antioxidant activity and production of phenolics, flavonoids, proanthocyanidins, and saponins were assessed. Unexpectedly, the coir dust supply did not favor the growth and production of secondary metabolites, as the best results were observed in plants grown in S3. Moreover, S3 is efficient in optimizing the growth, metabolite content, and antioxidant capacity of P. alata foliar extracts dispensing coir dust supplementation in the substrate. Therefore, adding coir to CSS is not recommended to enhance the production of secondary metabolites and the growth of P. alata seedlings.