The first classification of Carnatic ragas into mELakarta system dates back to 17th century, pioneered by Sri Venkatamakhi. The classification was made, considering 16 shades or variants of saptaswaras (unlike the 12 variants of Hindustani system) and hence as much as 72 distinct melakarta or Janaka/parent ragas were formed. Each parent/ Janaka raga has a number of Janya ragas or derivative ragas. It is estimated that there are as much as 75000 or even more different and distinct ragas in Carnatic system.
The following self explanatory chart depicts all the 72 mELakarta rAgAs, with their corresponding swaras.
Image Ref: Wikipedia