Flavonoids are phenolic compounds that differ in their chemical structure, have 15 carbon atoms in the C6-C3-C6 form, based on the nucleus of two benzene rings, A and B, attached to apyran ring, C (Figure 1).

Among "pyran series," compound 36 demonstrated the most interesting inhibitory effect showing 15 [micro]M MIC value; derivative 35 was able to interfere with the NF-[kappa]B/DNA interaction at 35 [micro]M MIC.

In addition to lapachol (2, Figure 1), different structural types of naphthoquinones, such aspyran and furanonaphthoquinones, are found in Bignoniaceae [18, 19] and disclose abroad spectrum of biological activities, including antitumor [20-23], trypanocidal [24], anti-inflammatory [7], antifungal [25], and antiparasitic activities [26-33].

A total of 16 volatile compounds with known antimicrobial and antioxidant properties, such as alcohol, ketone, aliphatic acid, benzene compound, hydrocarbon, furan, andpyran derivatives, have been identified, and the best antibacterial activity has been demonstrated by the fraction GCF3 (5 mg/ml) [11].

One is the ring-opening reaction of the depolymerized xylan unit through the cleavage of the hemiacetal bond (between oxygen and C-1 on thepyran ring), followed by dehydration between the hydroxyl groups on the C2 and C5 positions.

The reaction mixture was subjected to the reaction with [BF.sub.3] in C[H.sub.2][Cl.sub.2] for intramolecular closure of thepyran ring.

In addition, chromone (a derivative of benzopyran with a substituted keto group on thepyran ring), dinorxanthane sesquiterpene, and other substances isolated from T.