Qualitative phytochemical assays are very inaccurate. It is more accurate to use an instrumental technique (analytical) to decide if a particular compound is present or absent.

Nicholas-Sadgrove thank you very much

What do you mean by qualitative,

The concentration of the compound in the crude extract may be low to be detected as compared to individual compound isolated (matrix interferance)

This has to do with the sensitivity of the detection technique. That is, the minimum concentration that can be identified qualitatively. Most methods used for phytochemical analysis have low sensitivity and won't be able to detect very low concentrations of chemical groups present in the plant extract.

possibly the concentration was too low to be detected.