Effect of Trigonella foenum-graecum L. development stages on some phytochemicals content and allelopathic potential

• Developmental stage influences fenugreek bioactive compounds accumulation.
• Vegetative stage was the richest for phytochemicals assessed in aqueous extracts.
• Fruiting stage was the richest for phytochemicals assessed in organic fractions.
• Fenugreek aerial parts at vegetative stage had the strongest allelopathic potential.
• Germination and shoot were negatively correlated with alkaloids while root growth with polyphenols and flavonoids.

This study was conducted to evaluate the phytochemical content and allelopathic potential fenugreek aerial part, which was evaluated on lettuce germination and seedling growth, of as influenced by fenugreek developmental stages (vegetative, flowering and fruiting). The total phenolics, flavonoids, flavonols and flavones, alkaloids and proanthocyanidins contents in the aqueous extracts were lower in the fruiting stage in comparison with the vegetative stage. Among organic extracts, methanol extracts were the richest, and the vegetative and fruiting stages were the richest in the phytochemicals assayed. For allelopathic activity, all aqueous and organic extracts significantly delayed germination, reduced its rate and affected seedling growth. In addition, the analysis using WESIA software showed a stronger inhibition index of the aqueous extracts of aerial parts harvested at vegetative stage compared to the two other stages. Ethyl acetate and methanol fractions of aerial parts harvested at fruiting stage were the most toxic, respectively for lettuce germination and seedling growth. Significant negative correlation was found between germination and shoot growth and alkaloids content (R2 = 0.9). Similarly root growth was negatively correlated with polyphenols and flavonoids content (R2 = 0.98). Knowing the development stage, at which plants are most rich in allelochemicals, would counteract the allelochemical production in very small quantities so make full use allelopathic potential at the most appropriate time.