The former U23 world champion from the Colombia-Coldeportes team took his first victory on European soil this season as he beat compatriot Miguel Angel Rubiano to the line in an uphill finish.
Rubiano, Nairo Quintana, Xabier Zandio, Paolo Ciavatta, Gianluca Brambilla, Duber Quintero, Stefano Borchi, Frederico Rocchetti, Sergio Laganà, Luca Dodi and Henry Frusto were involved in an early break and built up a lead of 1:40 as the peloton did six laps of a 21.5km circuit.
But that advantage was quickly reduced and the lead group diminished to six: Androni duo Rubiano and Sella, Quintero (Colombia-Coldeportes), Team Sky's Nordhaug (SKY), Ciavatta (Acqua & Sapone) and Proni (Farnese Vini).
They were caught inside the final 30km as the action intensified on four concluding laps of a 12.2km circuit.
But the indefatigable Rubiano went on another attack, joined by Matteo Rabottini, Patrik Sinkewitz, Giovanni Visconti, Francesco Failli and Duarte.
The sextet stayed clear and it was Duarte who powered away on the uphill ramp to the finishing line with Farnese Vini-Selle Italia's Rabottini completing the podium.
- Nairo Quintana