The decisive score was beautifully created by Toulouse who didn't panic when trailing late on. Instead they fashioned a neat blindside move which saw Matanavou flip the ball inside for Poitrenaud to score.
The ball went at least a yard forward and it was debatable whether the pass had initially gone forward or gone backwards off Dave Lewis' outstretched fingers. The officials plumped for the latter.
It was harsh on Gloucester who had more than matched Europe's finest with Henry Trinder's 70th minute try seemingly set to earn the win.
However, Toulouse haven't won this tournament four times in the past without learning a thing or two about squeaking through in tight situations and they used every bit of that experience.
Although obviously desperately disappointed to be pipped at the post, Gloucester will take great heart from having matched up so well to the star studded current leaders of the French Top 14 and look to carry the recent good form into next weekend's home tie against Harlequins.
Gloucester had to make late changes to the announced line up. Olly Morgan was ruled out with a shoulder injury so Jonny May took over at full back. Lesley Vainikolo came on to the bench.
Meanwhile, Tom Savage failed a pre match fitness test on a leg injury and was replaced by Brett Deacon.
Freddie Burns kicked off Gloucester with the stadium resounding to the sounds of "Rouge et noir" and the Cherry and White's 2011-12 Heineken Cup campaign was underway.
And there was an early moral boost within 3 minutes as the pack won a penalty at a Toulouse scrum but Freddie Burns dragged the kick wide left.
The home side were quickly on to the front foot and Donguy was almost away down the left hand flank only for a try saving tackle from Mike Tindall. Quick ball gave Matanavou a chance on the other flank but the scramble defence just got to him.
There was huge pressure on Gloucester but a McAlister knock handed back possession and Burns cleared well.
With some decent territory, Gloucester stole a Toulouse line out and threatened briefly through May only for Nyanga to get caught offside. Burns made no mistake for a 3-0 lead.
It had been a good spell for Gloucester but a missed touch led to an opportunity for McAlister on 16 minutes as a man came in at the side after a Poitrenaud counter attack but, into the wind, the Kiwi drilled his kick wide.
Gloucester continued to keep up the pressure and very nearly conjured up a try when Freddie Burns chip bounced awkwardly near the Toulouse line but Akapusi Qera just couldn't gather the loose ball.
The home side then thought they'd scored as they turned the ball over after Jonny May ran the ball out from his own 22 but they had won the ball illegally and the stadium erupted into a cacophony of boos.
The crowd were starting to grow impatient as the half hour passed and a moment of genius from Henry Trinder almost resulted in s score but the centre knocked on trying to regather.
It was a brief respite. Gloucester won a turnover at the Toulouse scrum, moved the ball wide and May put Sharples over for the game's first try. Burns converted for 10-0.
With only a few minutes until half time, discipline was needed but a penalty was conceded from the restart and McAlister got Toulouse onto the scoreboard.
Worse followed as more indiscipline allowed the home team to move into the Gloucester 22 and McAlister slid a kick in behind the defensive line for Matanavou to score.
It was possibly controversial as Nyanga seemed to keep the ball in play with his arm in touch during the build up but the touch judge saw nothing wrong and he did have the best view so the try stood.
McAlister's conversion held up in the wind but the home side were back in the hunt at 10-8 at half time.
It was a cruel final few minutes for Gloucester who were well worthy of their 10-0 lead just moments later but it only takes an instant for a side of Toulouse's class to strike.
The second half would also see the home side with the wind at their backs so a tough second half lay ahead of the Cherry and Whites.
The pressure was quickly onto Gloucester but they defended stoutly for the opening few minutes although gaining possession was proving to be difficult in the face of the red and black onslaught although one spectacular catch and kick downfield from Charlie Sharples relieved some pressure.
McAlister was starting to ask real questions with his offloading game and the pressure eventually told. Alasdair Strokosch was penalised for knocking the ball out of the scrum half's hands and McAlister slotted the penalty for 11-10.
Burns had an immediate chance to regain the lead but, perhaps trying to strike it too hard into the wind, was just off target with a 55th minute penalty.
Gloucester then dodged a real bullet as Nyanga burst clear from a quick tap free kick. The supporting Burgess almost made the line but the overlap was on as the ball was switched left only for DOnguy to knock on with the line beckoning.
Poirenaud was then denied a score as referee Fitzgibbon saw a forward pass and Stade Ernest Wallon almost erupted in Gallic indignation.
The pressure was incessant but Gloucester defended their own line magnificently and Lionel Beauxis eventually opted for a 63rd minute drop goal only to push it wide.
After so much superb defence, it was a real let down to concede a penalty at a set scrum and Beauxis made no mistake for 14-10 after 66 minutes.
Back came the Cherry and Whites. With the referee playing advantage, Mike Tindall spotted a gap, made a half break and Henry Trinder took the offload to take a great angle to the line. Burns, under real pressure, converted for 17-14 to Gloucester.
The Gloucester supporters rejoiced and were still in full voice when Toulouse hit back, patiently working their way into a position to strike and Matanavou's sprint down the right touchline saw him transfer a forward looking pass inside to Poitrenaud who dived over. Lionel Beauxis kicked a fine conversion to rub salt into the wounds.
Gloucester did have a last opportunity to go for the win but, 50 metres out and playing into the win, pragmatism won the day and the ball was hoofed off the pitch to secure the losing bonus point.
It had been a fine game with both teams playing at real pace. Toulouse will probably feel that they weren't at their best but, to be fair, Gloucester's performance knocked them out of their stride.
The Cherry and Whites scored two excellent tries, defended doggedly and never looked like being overrun. However, they will probably rue the eight points conceded just before half time and a couple of near misses near the Toulouse line in the first half.
Defeat is always disappointing but so many positives can be taken from this one.
|Toulouse Score Card|
|Gloucester Rugby Score Card|