Eduan, Simbine shine at world relays
Eduan produced a thrilling final leg to outpace Jamaica's Shericka Jackson and Twanisha Terry of the United States for gold along with teammates Nia Wedderburn-Goodison, Amy Hunt and Bianca Williams.
"I did not think too much of (the) others, I just knew that if I gave all myself in, it would come out all right," said Eduan.
"I have a mentality of a winner, I don't care if Shericka or Shelly-Ann (Fraser-Pryce), respect to them, are running. I am going to give my all and I'm going to pass them and I'm going to win. And we did that!"
Spain snatched a shock silver in 42.28sec, with the Jamaican quartet also featuring multi-medalled Fraser-Pryce taking bronze (42.33), just five-hundredths ahead of the US team.
"We came out, took the chance, got a medal, qualified for the world championship in Tokyo," said Fraser-Pryce, whose first Olympic gold medal was at the 2008 Beijing Games.
"All in all we are very pleased. We are grateful for getting a bronze medal, and we will leave the fight for another day."
South Africa had in-form Simbine, winner of the two opening Diamond League 100m races this season, to thank for an electric anchor leg as he powered past Brandon Hicklin for gold in the men's 4x100m relay.
The team also featuring Bayanda Walaza, Sinesipho Dambile and Bradley Nkoana clocked a world leading time of 37.61sec.
The US took silver in 37.66sec, with Canada, featuring the same quartet who won gold in last year's Paris Olympics, claiming bronze.
"Once I got the baton I saw that US (were) in front of us, I just said to myself 'I need to catch the guy in front'," said Simbine.
"I knew I could do it, and I just chased him. I feed from chasing, I feed from being able to chase. So it's really great to be able to be in that position and get through it and get to the line first."
'My biggest dream'
There was another upset in the women's 4x400m relay, with Spain pushing the US team, the defending Olympic champions, into second.
Spanish anchor leg Blanca Hervas was overtaken on the final lap but she held her nerve to slowly reel back in a flagging Bailey Lear.
Paula Sevilla ran the first leg for Spain, just minutes after taking part in the 4x100m relay, with Eva Santidrian and Daniela Fra completing the winning line-up as they timed 3:24.13.
The US took silver in 3:24.72 with South Africa rounding out the podium in 3:24.84.
"Myself and all of them never felt like this before," said Hervas. "We are crazy excited -- gold medal, world relays champion, national record, everything -- my biggest dream, I am so thankful."
The South Africans brought two days of competition -- which also served as qualifiers for the world athletics championships in Tokyo in September -- to an end with gold in the men's 4x400m relay.
The quartet of Gardeo Isaacs, Udeme Okon, Leendert Koekemoer and Zakithi Nene raced home in 2:57.50.
Alexander Doom produced his trademark late push to guarantee silver for Belgium in 2:58.19, with Botswana taking bronze (2:58.27).
The US foursome of Chris Robinson, Courtney Okolo, Johnnie Blockburger and Lynna Irby-Jackson earlier claimed gold in the mixed 4x400m relay in a championship record of 3:09.54.
And the Canadian quartet of Sade McCreath, Marie-Eloise Leclair, Duan Asemota and Eliezer Adjibi topped the podium ahead of Jamaica and Britain in the mixed 4x100m relay, winning the first ever holding of the event in 40.30sec.