Royal jelly (RJ) is a well-known functional and medicinal food for human health promotion. Major royal jelly proteins (MRJPs), which are the major protein components in RJ, exhibit antimicrobial activities. However, the identities of the MRJPs of RJ responsible for its antioxidant effects have remained unclear. Here, we report that honeybee (Apis cerana) MRJP 2 (AcMRJP2) acts as an antimicrobial and antioxidant agent in RJ. Using recombinant AcMRJP2, which was produced in baculovirus-infected insect cells, we established the antimicrobial and antioxidant roles of MRJP 2. AcMRJP2 bound to the surfaces of bacteria, fungi, and yeast, which then induced structural damage in the microbial cell walls and led to a broad spectrum of antimicrobial activities. AcMRJP2 protected mammalian and insect cells via the direct shielding of the cell against oxidative stress, which led to reduced levels of caspase-3 activity and oxidative stress-induced cell apoptosis, followed by increased cell viability. Moreover, AcMRJP2 exhibited DNA protection activity against reactive oxygen species (ROS). Our data indicate that AcMRJP2 could play a crucial role as an antimicrobial agent and antioxidant in RJ, suggesting that MRJP 2 is a component responsible for the antimicrobial and antioxidant activities of RJ.

Major royal jelly proteins (MRJPs), important protein components of bee royal jelly (RJ) and exclusive nourishments for queen, exhibit various biological and pharmacological activities. RJ is one of the most studied bee products, but the crucial roles for MRJP2 as an antimicrobial and antioxidant agents remain largely unknown. Here we demonstrated the antimicrobial and antioxidant functions of the Asiatic honeybee (Apis cerna) MRJP2 (AcMRJP2). Recombinant AcMRJP2 of approximately 53 kDa was expressed in baculovirus-infected insect cells, and it exhibited antimicrobial activity against bacteria, fungi, and yeast via binding to microbial surfaces and inducing structural damage in microbial cell walls. AcMRJP2 protected mammalian and insect cells against oxidative damage through shielding of cell membranes. Interestingly, AcMRJP2 exhibited DNA protection activity and DPPH radical-scavenging activity. Altogether, our data demonstrated that AcMRJP2 functions as antimicrobial and antioxidant agents.