Nostoflan, an acidic polysaccharide from Nostoc flagelliforme that exhibits potent virucidal activity against herpes simplex virus-1, is also noteworthy. Currently, two carbohydrate-binding proteins, namely, cyanovirin-N and scytovirin, are being developed as potent virucidal drugs. These carbohydrate-binding proteins show antiviral activity by interfering with multiple steps in the viral fusion process.