Balsam fir foliage

In guinea pigs, oral administration of abietic acid (an abietane diterpenoid found in the oleoresin) produced antiallergic activity. In vitro inhibition of 5-Upoxygenase by abietic acid may be a contributing factor to the activity. The essential oil (balsam fir oil) extracted from the foliage has shown in vitro cytoxicity against several tumor cell lines. The main active constituent was identified as a-humulene. ... 

In comparison to associated species, black spruce is relatively pest resistant. Black spmce is less susceptible to spmce budworm (Choristoneura fumiferana [Clem.]) than white spmce and balsam fir, possibly due to its late bud flush (Blais, 1957), but is also less susceptible to spmce budworm than red spmce, another species exhibiting a late bud flush (Manley and Fowler, 1969 Osawa, 1989). Whereas spmce budworm feeds on both foliage and cones of white spmce, when on black spmce, it prefers the cones (Prevost, 1990). Manley and Fowler (1969) speculated that resistance to spmce budworm is polygenic, as segregation was not apparent in red x black spmce hybrids. 

---