**4. Discussions**

#### **4.1 Discussions regarding in vitro test**

So, the overall in vitro antioxidant assay could be concluded that the obtained crystal compound (may be piperine) may have strong antioxidant power. By comparing with standard compound (catechin, ascorbic acid), the prediction could be extended that the black pepper is a great source of antioxidant compound with specifying the crystal constituent (may be piperine) as a prominent free radical scavenger.
