Table 1. Common Linkages in Lignin and Their Presence in Softwood and Hardwood

Type	Bonds	Frequency in softwood (%)	Frequency in hardwood (%)
β-aryl-ether	β-O-4’	35-60	50-70
Diaryl ether	4-O-5’	< 4	~7
Dihydroxy biphenyl	5-5’	10	~5
Phenyl coumarane	β-5’	11-12	4-9
Pinoresinol	β-β’	2-3	3-4