The 18-year-old Das, a favourite to win gold, clocked 52.25 seconds to win heat number four and lead the time charts. Running at lane number three, Das beat Stacey-Ann Williams of Jamaica (52.71) in the fastest of the five heats.
Another Indian, Jisna Mathew also qualified for the semifinals by winning the fifth heat in 54.32 seconds.
American Taylor Manson, a medal contender, finished overall second with a time of 52.68 seconds. She won heat number one.
The first four finishers in each heat and the next four fastest qualify for the semifinals which will be run tomorrow.
Das is a favourite to win gold as she is the U-20 season leader in this quartermile event. If the Assam girl happens to win gold, she will become the first Indian athlete to do so in a track event in an U-20 World Championships.
Das clocked an Indian U-20 record of 51.32 seconds to finish sixth in the Commonwealth Games 400m final in Gold Coast in April. Since then, she has gone onto improving her timings. She lowered the Indian U-20 record in 400m to 51.13 seconds while winning gold in the recent National Inter State Championships in Guwahati.
M Shreeshankar finished fourth in the qualification round of men's long jump event with an effort of 7.68m to make it to the final round. Compatriot Lokesh Satyanathan, however, finished 17th with a jump of 7.31m.
In men's shot put, Asish Bholothia finished eighth in Group A qualification round with a personal best throw of 18.62m but that was not enough to make it to the final round.
India is being represented by 31 athletes at the six-day championship.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)