Like his brother in law, Arellano was an active Freemason, hailing from Logia Lusong No. 185.[9] Buan was his masonic name.[9] He also solicited funds for Filipino expatriates in Spain when del Pilar had to flee to Spain, because of allegedly subversive articles that appeared in the Filipino newspaper that del Pilar published, the Diariong Tagalog (Tagalog Newspaper).[11] He was also part of the short-lived La Propaganda, a movement founded by his brother-in-law del Pilar and Mariano Ponce, which sought reforms in the political landscape of the Philippines.[4]
During the undisclosed October 1892 meeting of the Katipunan, Arellano was elected the first president of its Supreme Council and the first to be given the title Supremo.[17][4] During his term as president, he endorsed the Katipunan's laws developed by its members particularly Plata and Diwa.[4] In February 1893, Bonifacio saw Arellano as ineffective in leading the secret organization, thus, Roman Basa replaced him and became the second Supremo.[4] In spite of his removal as president, Arellano respectfully continued to be active in the movement.[4] He organized provincial councils in Bulacan during the same time Bonifacio and other members also organized councils in Manila, as a result, they attained one of the goals of Rizal in forming the Liga.[4]
Later life and death
Arellano brought back the Liga in April 1893 to keep up the efforts of Rizal, despite not being present with them.[4] Juan de Zulueta helped him to reestablish the Liga and they elected new set of officers with Arellano getting the secretary and treasurer positions.[4] Although, the Liga was later dissolved lasting only six months.[4] Three years later, on October 10, 1896, he was arrested[4] and later jailed and then went back to his hometown in Bulacan.[9] When the revolution broke out in August 1896, he joined the brigade of Gregorio del Pilar,[9] his nephew,[20] becoming its commissary officer. Although in some historians, his life after his arrest is vague but they inclined to believe that Arellano did join his nephew's brigade.[4]
He fought in the battles in Bulacan during the Philippine–American War, but he contracted tuberculosis in the course of the war and died of the disease while he and his fellow revolutionists were fighting in the Cordillera Mountains.[7] His comrades buried him in the town cemetery of La Trinidad, Benguet.[7] There are sources saying that he died of tuberculosis on October 7, 1899[9] but as previously mentioned, his life after his arrest in 1896 remains unclear.[4] There are historians who hold that after Arellano was named by Katipunan members who were apprehended by the Spaniards and forced to reveal information, he was eventually arrested too, then tortured and finally abandoned to die.[4]