Punjab National Bank (PNB) has reported over three-fold jump in net profit to Rs 2,223 crore in the Dec quarter – the highest in the last 15 quarters – on the back of higher interest income and improved asset quality. The bank had earned a net profit of Rs 629 crore in the same quarter a year ago. Its total income increased to Rs 29,962 crore during the quarter under review against Rs 25,722 crore in the same period last year, PNB said.