Saina, the London Olympics bronze medallist, defeated eighth-seed South Korea's An Se Young 25-23, 21-12 in a match that lasted for 39 minutes.
In the first game, Saina was made to work hard by the 17-year-old as both the shuttlers kept going at each other. But, it was the Indian who had the last laugh and ultimately won the game 25-23.
The Hyderabad shuttler, however, didn''t have to sweat too much in the second game as she won comfortably by a 21-12 margin to enter the last eight of the competition. Saina will now face Rio Olympic gold medallist Carolina Marin of Spain.
Sindhu also easily got the better of Japan's Aya Ohori winning the match 21-10, 21-15 in just 34 minutes. After a one-sided contest in the first game, the Japanese showed some improvement but it wasn't enough to stop an experienced Sindhu in the next game.
On the other hand, Sameer went down in a hard-fought battle against Malaysia's Lee Zii Jia. The Indian missed a quarter-final berth narrowly as he suffered a 21-19, 21-20 loss in a closely fought match, lasting for 52 minutes.
Prannoy too, bowed out after going down 21-14, 21-16 to ace Japanese shuttler Kento Momota in the 45-minute affair.
( With inputs from IANS )