Hi Syed

According to me, you can not call miRNAs as phytocompounds as they themselves do not produce any protein, they are non coding RNAs.. Instead they regulate various gene pathways by targeting one/more genes, either by cleaving the transcript (most likely in plants) or by translational repression. 

They are kind of mediators in controlling various developmental processes in the plants. To get a better understanding of how miRNAs work, you can refer to some recent papers.

I hope it helps.

@Swati

I agree with you but mi or siRNAs can be classified as phtochemicals

Sir

But they don't code for any proteins directly, then how can we consider them as phytochemicals?

Highly agreed with both answers of Swati Megha.

I believe phytochemicals are primary or secondary metabolites in a plant cells. As far as I know, proteins and nucleic acid do nott fall into this category. They are no different in their basic structure from normal RNAs so I wont classify them as phytochemicals.