Composition and bioactivity of propolis derived from New Zealand native forest

New Zealand's unique indigenous flora has evolved due to its geographical isolation in the Southern Hemisphere. In the 250 years, since European colonisation commenced, much indigenous flora has been replaced by plants largely of Northern Hemisphere origin including poplar species and pine. There are however still a few large areas of principally native flora. The honeybee (Apis mellifera) was introduced to New Zealand in 1839, so has no evolutionary link to the New Zealand indigenous flora. New Zealand propolis from areas in which honeybees have access to poplar and other Northern Hemisphere species is similar in chemical profile to Northern Hemisphere propolis. However, when honeybees were placed in an extensive area of native flora, Te Urewera in the North Island,the chemical profile of propolis produced was vastly different. This “endemic” propolis was characterised by the presence of diterpenoids in contrast to the flavonoids found in poplar-type propolis. These diterpenoids, isocupressic acid, acetyl isocupressic acid, manool, torulosal, communic acid and ferruginol, were characterised by GC–MS and by NMR spectroscopy of the isolated compounds. The “endemic” propolis has commonality with propolis of the Mediterranean-type as well as some Brazilian propolis. Investigation of the bioactivity of a sample of the “endemic” propolis revealed good antioxidant behaviour with a TEAC of 1481 mg_trolox g⁻¹, dose-dependent inhibition of mitochondrial dehydrogenase activity, inhibition of superoxide production with an IC₅₀ of 262 μg mL⁻¹ and inhibition of methicillin resistant and methicillin sensitive S. aureus. Much of this bioactivity can be attributed to the presence of the diterpenoids.