Trippe Olympic bronze medalist De Grasse would have been celebrating a personal best if the strong +4.8m/s tail wind did not not exceeded the permitted limit of 2.0m/s.
It was also a third straight Diamond League victory for the 22-year-old De Grasse.
"I am very happy to have won despite the wind. I feel that I'm improving year after year. But these are only preparations for the big show of the worlds."
"That's the fastest I've ever run, it's going to be a shock to the body. Tomorrow's going to hurt a little bit, but I’m just looking forward to the next race and see what I can do legally." said De Grasse.
Kenya’s Timothy Cheruiyot smashed the men's 1500m world lead with 3:30.77. Meanwhile defending world champion Asbel Kiprop set his season’s best of 3:33.17 to take 4th. Norway's 16-year-old Jakob Ingebrigtsen took more than two seconds off his 1500m personal best to set a European U18 best of 3:39.92.
Norway's Karsten Warholm took the men's 400m hurdles in 48.82sec. It was a second second consecutive Diamond League victory for the Norwegian hurdler.
Bahamas Steven Gardiner impressed with 44.58sec for the win in the men's 400m.
SA's Antonio Alkana and Britain's Andrew Pozzi were disqualified for false starting in the men's 110m hurdles. Spain's Orlando Ortega edged defending world champion Sergey Shubenkov for the win clocking 13.09sec (+3.3m/s)
Manyonga led South African 1-2 victory in the men's long jump with wind assisted 8.36m (+3.3m/s) leap. Rushwal Samaai took second with 8.29m (+1.3m/s) jump.
Jamaica's Fedrick Dacres celebrated victory in the men's discus with 68.36m throw.
Murielle Ahoure (CIV) took the women's 22.68 beating Canada's Crystal Emmanuel by only 0.01sec.
In the women's discus, Yaime Perez of Cuba threw 67.92m to beat world and Olympic champion Sandra Perkovic of Croatia (67.75m).
Francine Niyonsaba clocked 1:59.11 for the win in the women's 800m.