Clara Ponsatí, a former education minister in the Catalan regional government, lives and works in St Andrews but faces arrest, a court appearance and extradition to Spain for her part in the failed attempt to secure independence for the region past year.
European arrest warrants were reissued last Friday for Ponsati and five other secessionist figures who fled Spain, including former President Carles Puigdemont.
"Scotland has been a true friend to Catalonia in her darkest hours", said Anwar.
Clara Ponsati, Catalonia's former education chief, is preparing a "robust" legal challenge to the charges, stemming from her role in Catalonia's unsuccessful effort to declare independence from Spain.
The former education minister is sought by Madrid on charges of "violent rebellion and misappropriation of public funds" regarding her role in Catalonia's October independence referendum.
"Clara views these charges as "political persecution" and submits that her human rights and justice can not be guaranteed in the Spanish Courts".
An online crowdfunding drive to raise money for Professor Ponsati's extradition defence had exceeded £174,000 by 5pm on Wednesday.
"She submits that Spain has not followed due process, can not guarantee the independence of the judiciary and has repeatedly abused the human rights of the Catalan people".More news: California sues Trump administration over citizenship query in census
In a prepared statement delivered to press outside of the police station, Anwar said: "After we enter the police office my client will be formally placed under arrest".
Ponsati was a minister in the Catalan government when it declared independence from the rest of Spain following a referendum in October.
Despite his detention, the separatist-controlled Catalan parliament on Wednesday defended Puigdemont's right to be a candidate again to head the regional government.
Mr Anwar said of Prof Ponsati: 'She is truly humbled by the support she has received from across Scotland as well as that of the Scottish Government, but believes that it is right that our courts must now decide what happens next'.
Earlier, First Minister Nicola Sturgeon said the Scottish Government "supports the right of the people of Catalonia to determine their own future and that we strongly oppose the Spanish Government's decision to seek the arrest and imprisonment of independence supporting politicians". He is being held in prison pending an extradition hearing in a German court.
She fled later that month with Puigdemont and three other former ministers to Brussels, after Spain dismissed the Catalan executive and imposed direct rule.
She had resumed working at the University of St Andrews in Fife.
Ms Ponsati's lawyer told the BBC yesterday that they would be challenging the rebellion charge, insisting that there was no similar crime in Scotland and that "the only people responsible for violence on [referendum] day were the Spanish police".