The present invention provides a method of isolating at least one ingredient with anti-viral efficacy from Baphicacanthus cusia. The ingredient can be an alkaloid, a triterpenoid, a lignan, a phenylethanoid, a sesquiterpene lactone, or a flavonoid. Two new alkaloids are produced, which have not been previously reported. Moreover, the method isolates 12 compounds which could not or have not been previously isolated. A pharmaceutical composition includes the at least one ingredient and at least one pharmaceutical tolerable excipient. A method of treating a subject suffering from a viral disease includes administering at least one ingredient isolated from Baphicacanthus cusia.