We try to extract DNA from curry leaves (Murraya koenigii) using ctab method but after the washing of step we are having a brown colour depoist and its inhibiting our PCR process. This happen to samples which are stored in -20°c (at least 1 month) but not to fresh leaves. Then we used the pro omega plant DNA extraction kit and still we have the issue for stored samples. Would please anyone help me as we are closing to deadline.