World No 56 Prannoy, who had a fine outing in the Indian Badminton League last month, again punched above his weight, to beat Denmark's Jan O Jorgensen, ranked ninth, 21-14, 13-21, 21-17, in a 53-minute match.
Srikanth, who has also acquired a giant-killing reputation after his recent exploits, defeated Japan's Kazuteru Kozai 21-12, 21-16 in just 30 minutes in another men's singles match.
Ajay Jayaram also made it to the last eight after a 21-13, 11-21, 21-18 victory over Japan's Yuichi Ikeda.
He will next take on fifth seed Tien Minh Nguyen of Vietnam.
Another Indian in the fray, Anand Pawar went down tamely to world No 1 Chong Wei Lee of Malaysia 21-12, 21-16 in just 34 minutes.
Eighth seeded Sindhu was beaten 6-21, 17-21 by local shuttler Akane Yamaguchi in 32 minutes, in the women’s singles.
India's men's doubles pair of Manu Attri and Sumeeth Reddy B also fell by the wayside, losing to the more experienced combo of fourth seeded Chinese Xiaolong Liu and Zihan Qiu 17-21, 16-21 in 36 minutes.
The highlight of the day for India, though, was Prannoy's gritty performance. He rode on his mighty smashes and energetic display at the net to tame the 25-year-old Dane, who won the silver medal at 2010 European Badminton Championships.
Down 1-4, Prannoy soon erased the deficit and caught up with Jorgensen at 9-9. He then used his smashes to good effect to take the first game.
In the second, Jorgensen again opened up a slender 4-2 lead and though the Indian clawed back, the Dane was successful in breaking the deadlock at 9-9 and maintaining the distance to level the scores.
In the decider, it was Prannoy who snatched the early lead which he held on to despite Jorgensen’s strong fightback.
Leading 18-17, Prannoy grabbed the next three points to enter the quarter-finals.
Prannoy, who won the silver in the boys' singles at the 2010 Youth Olympics, is in good since making a comeback after being out of action due to an injury.
The 21-year-old had beaten some big names, including Thailand's Boonsak Ponsana, in Swiss Open Grand Prix Gold, and Taufik Hidayat, at the India Open.
Image: H S Prannoy
Photograph: Indian Badminton League